Second to Hour Converter
Convert seconds to hours with our free online time converter.
Quick Answer
1 Second = 0.000278 hours
Formula: Second × conversion factor = Hour
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Second to Hour Calculator
How to Use the Second to Hour Calculator:
- Enter the value you want to convert in the 'From' field (Second).
- The converted value in Hour will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Time category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Second to Hour: Step-by-Step Guide
Converting Second to Hour involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Second = 0.000277778 hoursExample Calculation:
Convert 60 seconds: 60 × 0.000277778 = 0.0166667 hours
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.
Need to convert to other time units?
View all Time conversions →What is a Second and a Hour?
What Is a Second?
The second (symbol: s) is the SI base unit of time, defined with extraordinary precision using atomic physics rather than astronomical observations.
Official SI definition (since 1967): The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom at absolute zero temperature and at rest.
In simpler terms:
- Caesium-133 atoms oscillate at a precise frequency when energized
- One second equals exactly 9,192,631,770 of these oscillations
- This provides a natural, unchanging standard independent of Earth's rotation
Why this matters: This atomic definition provides accuracy to better than 1 second in 100 million years for modern atomic clocks, enabling:
- GPS navigation (accuracy requires nanosecond precision)
- Global telecommunications synchronization
- Scientific experiments requiring extreme precision
- Financial transaction timestamps
- Internet infrastructure coordination
Second vs. Other Time Units
Subdivisions of the second:
- 1 decisecond (ds) = 0.1 s = 10⁻¹ s (rarely used)
- 1 centisecond (cs) = 0.01 s = 10⁻² s (stopwatch hundredths)
- 1 millisecond (ms) = 0.001 s = 10⁻³ s (computer operations)
- 1 microsecond (μs) = 0.000001 s = 10⁻⁶ s (electronics, photography)
- 1 nanosecond (ns) = 0.000000001 s = 10⁻⁹ s (computer processors, GPS)
- 1 picosecond (ps) = 10⁻¹² s (laser physics, molecular vibrations)
- 1 femtosecond (fs) = 10⁻¹⁵ s (ultrafast lasers, chemical reactions)
Multiples of the second:
- 60 seconds = 1 minute
- 3,600 seconds = 1 hour
- 86,400 seconds = 1 day
- 604,800 seconds = 1 week
- 31,536,000 seconds = 1 year (365 days)
- 31,557,600 seconds = 1 Julian year (365.25 days)
The hour (symbol: h or hr) is a unit of time equal to 60 minutes, 3,600 seconds, or 1/24 of a day.
Official SI-derived definition: Since the second was redefined atomically in 1967, one hour equals exactly 3,600 seconds, where each second is 9,192,631,770 periods of caesium-133 radiation. Therefore:
- 1 hour = 3,600 × 9,192,631,770 = 33,074,688,259,200,000 caesium-133 oscillations
- This equals approximately 33.07 quadrillion atomic oscillations
Practical conversions:
- 1 hour = 60 minutes (exact)
- 1 hour = 3,600 seconds (exact)
- 1 day = 24 hours (exact)
- 1 week = 168 hours (7 × 24)
- 1 year (365 days) = 8,760 hours (365 × 24)
The hour is not an SI base unit, but it is accepted for use with the SI due to its fundamental role in civil timekeeping and global coordination.
The 24-Hour Day
The division of the day into 24 hours reflects both astronomical reality and historical convention:
Astronomical basis:
- Earth rotates 360° in ~24 hours (one solar day)
- Each hour = 15° of rotation (360° ÷ 24 = 15°)
- This is why time zones are spaced ~15° longitude apart
- Solar noon occurs when the sun crosses the meridian (highest point)
Why 24, not 20 or 10?
- Ancient Egyptians used base-12 counting (duodecimal)
- 12 is highly divisible: factors are 1, 2, 3, 4, 6, 12
- 12 daytime hours + 12 nighttime hours = 24-hour cycle
- This system was inherited by Greeks, Romans, and eventually globally standardized
Solar vs. Sidereal Hours:
- Solar hour: Based on Earth's rotation relative to the Sun (24 hours per cycle)
- Sidereal hour: Based on Earth's rotation relative to distant stars (23 hours, 56 minutes, 4 seconds per cycle)
- Civil timekeeping uses solar hours because they align with day/night cycles
Note: The Second is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Hour belongs to the imperial/US customary system.
History of the Second and Hour
Ancient Origins: Babylonian Mathematics (3000 BCE)
The division of time into units of 60 has roots in ancient Babylonian sexagesimal (base-60) mathematics:
Why base-60?
- Highly divisible: 60 has divisors 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
- Finger counting: Babylonians counted 12 finger segments (phalanges) on one hand using the thumb, repeated 5 times for the other hand (12 × 5 = 60)
- Astronomical convenience: 360 days approximated the year (6 × 60), aligning with the 360-degree circle
Time divisions established:
- 1 day = 24 hours (2 × 12)
- 1 hour = 60 minutes
- 1 minute = 60 seconds
This system spread through ancient Egypt, Greece, and Rome, persisting for over 4,000 years.
Medieval Development: Mechanical Clocks (1200s-1600s)
The word "second" derives from Medieval Latin "pars minuta secunda" meaning "second minute part" (the second division of the hour):
- First division: Hour divided into 60 "pars minuta prima" (first minute parts) = minutes
- Second division: Minute divided into 60 "pars minuta secunda" (second minute parts) = seconds
Early mechanical clocks (1200s-1300s):
- Displayed only hours, no minute or second hands
- Too imprecise to measure seconds accurately
- Driven by falling weights and escapement mechanisms
Pendulum revolution (1656):
- Christiaan Huygens invented the pendulum clock
- First clocks accurate enough to measure seconds reliably
- Pendulum period provided regular "tick" for second counting
- Accuracy improved from 15 minutes/day to 15 seconds/day
Marine chronometers (1700s):
- John Harrison developed precise clocks for navigation (1730s-1760s)
- Accurate timekeeping enabled longitude determination at sea
- Precision to within 1 second per day
Astronomical Definition: Mean Solar Second (1832-1967)
In 1832, the second was formally defined as 1/86,400 of a mean solar day:
- Mean solar day: Average length of a solar day over a year (accounts for Earth's elliptical orbit)
- 86,400 seconds: 24 hours × 60 minutes × 60 seconds
Problems with astronomical definition:
- Earth's rotation is irregular: Tidal friction gradually slows rotation (~2 milliseconds per century)
- Seasonal variations: Earth's orbit affects day length by milliseconds
- Unpredictable fluctuations: Earthquakes, atmospheric changes affect rotation
- Increasing demand for precision: Radio, telecommunications, science required better accuracy
By the 1950s, astronomical observations showed the "second" was not constant—the length varied by parts per million depending on the era.
Atomic Revolution: Caesium Standard (1955-1967)
1955 - First caesium atomic clock:
- Louis Essen and Jack Parry at UK's National Physical Laboratory built the first caesium atomic clock
- Demonstrated caesium-133 atoms oscillate at precisely 9,192,631,770 Hz
- Accuracy: 1 second in 300 years (far exceeding astronomical clocks)
1967 - Official redefinition: The 13th General Conference on Weights and Measures (CGPM) redefined the second:
"The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom."
Why caesium-133?
- Atomic property: Transition frequency is a fundamental constant of nature
- Highly stable: Unaffected by temperature, pressure, or electromagnetic fields
- Reproducible: Any caesium-133 atom behaves identically
- Practical: Relatively easy to construct atomic clocks using caesium
Impact:
- Timekeeping became independent of Earth's rotation
- Precision improved from parts per million to parts per trillion
- Enabled GPS, internet synchronization, telecommunications, and modern science
Modern Atomic Clocks (1990s-Present)
Caesium fountain clocks (1990s):
- Atoms launched upward in "fountain" configuration
- Gravity slows atoms, allowing longer measurement time
- Accuracy: 1 second in 100 million years
Optical lattice clocks (2000s-2020s):
- Use strontium or ytterbium atoms instead of caesium
- Operate at optical frequencies (100,000× higher than caesium)
- Accuracy: 1 second in 15 billion years (age of the universe!)
- May redefine the second in future decades
Applications requiring atomic precision:
- GPS satellites: Nanosecond errors cause position errors of ~1 foot
- High-frequency trading: Microsecond timestamps for financial transactions
- Telecommunications: Synchronizing cell towers and internet infrastructure
- Science: Detecting gravitational waves, testing relativity, fundamental physics
Leap Seconds: Reconciling Atomic and Astronomical Time
The problem:
- Atomic time (TAI): Runs at constant rate based on caesium clocks
- Earth rotation (UT1): Slows gradually due to tidal friction
- Difference: ~2 milliseconds per day (accumulates ~1 second every 18 months)
Solution: Leap seconds (since 1972):
- Coordinated Universal Time (UTC) = atomic time adjusted to stay within 0.9 seconds of Earth rotation
- Leap second: Extra second added (or removed) on June 30 or December 31
- 27 leap seconds added between 1972-2016 (none since 2016)
Controversy:
- Leap seconds cause problems for computer systems, GPS, networks
- Debate ongoing about abolishing leap seconds in favor of pure atomic time
- Possible change may occur in the 2030s
of the Hour
Ancient Egyptian Origins (c. 2000 BCE)
The earliest systematic division of day and night into hours comes from ancient Egypt around 2000 BCE. Egyptian priests needed to schedule temple rituals and religious observations throughout the day and night.
Egyptian timekeeping innovations:
-
Shadow clocks (sundials): Used during daylight to track time by shadow position
- Divided daylight into 12 parts
- Earliest example: Obelisk shadow clock (c. 1500 BCE)
-
Water clocks (clepsydrae): Used at night and cloudy days
- Water dripped from container at constant rate
- Markings indicated elapsed time
- Divided nighttime into 12 parts
Crucial limitation: Seasonal hours (temporales horae)
- Summer daylight hours were longer than winter daylight hours
- Example: In Egypt, summer daytime hour ≈ 75 minutes, winter daytime hour ≈ 45 minutes
- Nighttime hours varied inversely (longer in winter, shorter in summer)
- This made sense for agricultural societies organized around daylight availability
Why 12 divisions?
- Egyptians used base-12 (duodecimal) counting, possibly because:
- 12 lunar months per year
- 12 knuckles on four fingers (excluding thumb)—convenient finger counting
- 12 is highly divisible (1, 2, 3, 4, 6, 12)
Greek and Roman Refinement (300 BCE - 400 CE)
Hellenistic astronomers (c. 300 BCE) introduced the concept of equal-length hours:
- "Equinoctial hours": Dividing the full 24-hour day-night cycle into 24 equal parts
- Each equinoctial hour = 1/24 of a mean solar day
- This was primarily used for astronomical calculations, not daily timekeeping
- Hipparchus (c. 150 BCE) used equinoctial hours for celestial observations
Roman timekeeping:
- Romans continued using seasonal hours for daily life
- Day (from sunrise to sunset) divided into 12 horae
- Night divided into 4 vigiliae (watches) of 3 hours each
- "First hour" (prima hora) = first hour after sunrise (varies by season)
- "Sixth hour" (sexta hora) = midday → origin of "siesta"
- "Eleventh hour" = last hour before sunset → modern idiom "at the eleventh hour" (last minute)
Roman water clocks (clepsydrae):
- Public water clocks in marketplaces
- Adjusted seasonally to maintain 12-hour daytime divisions
- Used for timing speeches in Senate (each senator allotted specific time)
Medieval Islamic Golden Age (700-1300 CE)
Islamic scholars made critical advances in precise timekeeping for astronomical observations and prayer time calculations:
Five daily prayers (salat):
- Fajr (dawn), Dhuhr (midday), Asr (afternoon), Maghrib (sunset), Isha (evening)
- Required accurate determination of solar positions
- Drove development of sophisticated astronomical clocks
Key innovations:
- Astronomical tables (zij): Calculated prayer times using equinoctial hours
- Astrolabes: Portable astronomical computers for time determination
- Advanced water clocks: Al-Jazari's "Castle Clock" (1206) featured complex automata
- Mathematical timekeeping: Used trigonometry to calculate hour angles
Islamic astronomers fully adopted equinoctial hours for scientific work while society continued using seasonal hours for daily activities.
Mechanical Clocks and Hour Standardization (1300-1600)
The invention of mechanical clocks in medieval Europe around 1280-1300 CE forced the adoption of equal-length hours:
Why mechanical clocks standardized hours:
- Mechanical escapement mechanisms tick at constant rates
- Cannot automatically adjust for seasonal variations
- Fixed 24-hour cycle physically built into clockwork
- This made equal-length hours the practical default
Early public clocks:
- Salisbury Cathedral Clock (England, c. 1386): Still running, one of oldest
- Wells Cathedral Clock (England, c. 1390): Features astronomical dial
- Prague Astronomical Clock (Czech Republic, 1410): Shows multiple time systems
- Church tower clocks visible/audible across towns
- Bells chimed on the hour, coordinating community activities
Impact on society:
- Transition from "task-oriented time" (work until task done) to "clock time" (work specific hours)
- Monasteries first adopted strict hour-based schedules (canonical hours)
- Urban merchants and craftsmen followed
- "Time discipline" emerged: punctuality became valued
Hour angles and navigation:
- 1 hour = 15° longitude (since Earth rotates 360° in 24 hours)
- Ships could determine longitude by comparing local solar noon to chronometer showing home port time
- This principle drove development of marine chronometers in 1700s
12-Hour vs. 24-Hour Time Notation
12-hour clock (with AM/PM):
- AM = ante meridiem (Latin: before midday)
- PM = post meridiem (Latin: after midday)
- Hours: 12:00 AM (midnight), 1 AM-11 AM, 12:00 PM (noon), 1 PM-11 PM
- Used in: United States, Canada, Australia, Philippines, parts of Latin America
- Ambiguity issue: 12:00 AM vs. 12:00 PM frequently confused
24-hour clock (military time):
- Hours numbered 00:00 (midnight) through 23:59
- Used in: Most of Europe, Asia, Africa, South America, military/aviation worldwide
- ISO 8601 international standard: HH:MM:SS format (e.g., 14:30:00)
- Eliminates AM/PM ambiguity
- Preferred for timetables, logistics, computing
Historical development:
- Ancient Egyptians and Romans used 1-12 numbering twice daily
- 24-hour notation emerged with astronomical use in Renaissance
- Military adoption (especially WWI era) standardized 24-hour format
- Computing systems use 24-hour format internally
Time Zones: Dividing Earth into Hours (1883-1884)
Before the late 1800s, each town kept its own "local solar time" based on the sun's position. This created chaos for railroad timetables—a train journey might cross dozens of different local times.
Railroad time standardization (1883):
- US/Canadian railroads established four continental time zones on November 18, 1883
- Each zone spanned roughly 15° longitude (one hour)
- Cities synchronized clocks within each zone
International Meridian Conference (1884, Washington D.C.):
- Established Greenwich, England as 0° longitude (Prime Meridian)
- Divided Earth into 24 standard time zones, each 15° wide
- Each zone offset by one hour from UTC (Coordinated Universal Time, formerly GMT)
- Created International Date Line at 180° longitude
Modern time zones:
- Standard zones: UTC-12 to UTC+14 (some zones offset by 30 or 45 minutes)
- Daylight Saving Time: Advances clocks 1 hour in summer in some regions
- Political boundaries: Zones follow country borders, not just longitude
- China uses single time zone (UTC+8) despite spanning 5 geographical zones
Atomic Era: Hours Defined by Seconds (1967-Present)
When the second was redefined atomically in 1967 based on caesium-133 oscillations, the hour inherited this precision:
1 hour = exactly 3,600 SI seconds = 33,074,688,259,200,000 caesium oscillations
Modern atomic clocks maintain this definition with extraordinary stability:
- Caesium fountain clocks: Accurate to 1 second in 100 million years
- Optical lattice clocks: Accurate to 1 second in 15 billion years (2019)
- GPS satellites: Each carries atomic clocks synchronized to nanoseconds
Leap seconds:
- Earth's rotation gradually slows (tidal friction)
- Occasionally, an extra second added to clock time to match Earth rotation
- 27 leap seconds added 1972-2016
- Controversy: May be abolished in favor of "leap hours" every few centuries
Common Uses and Applications: seconds vs hours
Explore the typical applications for both Second (imperial/US) and Hour (imperial/US) to understand their common contexts.
Common Uses for seconds
The second is the universal foundation for all time measurement in modern civilization:
1. Timekeeping and Clocks
Everyday timekeeping:
- Wristwatches and clocks display hours, minutes, seconds
- Smartphones synchronize to atomic time via network
- Wall clocks, alarm clocks, digital displays
- Public time displays (train stations, airports, town squares)
Precision timekeeping:
- Atomic clocks: Caesium, rubidium, hydrogen maser clocks
- GPS satellites: Carry atomic clocks for navigation
- Scientific facilities: National metrology institutes maintain primary time standards
- Network Time Protocol (NTP): Synchronizes computer clocks to microsecond accuracy
2. Scientific Research and Experiments
Physics experiments:
- Measuring particle lifetimes (nanoseconds to picoseconds)
- Timing light pulses in lasers (femtoseconds)
- Gravitational wave detection (millisecond timing precision)
- Quantum mechanics experiments (Planck time: 10⁻⁴⁴ seconds)
Chemistry:
- Reaction kinetics and rates
- Spectroscopy (measuring light absorption/emission frequencies)
- Femtochemistry (bond breaking/forming at femtosecond scale)
Biology:
- Neural signal timing (milliseconds)
- Cellular processes (seconds to hours)
- Ecological cycles (days, seasons, years measured in seconds)
3. Computing and Digital Systems
Processor operations:
- CPU clock speeds measured in GHz (billions of cycles/second)
- Instruction execution times (nanoseconds)
- Cache latency, memory access times
Software and programming:
- Timestamps (Unix time: seconds since January 1, 1970)
- Timeouts and delays
- Animation frame rates (60 frames/second = 0.0167 s/frame)
- Video frame rates (24, 30, 60 FPS)
Database and logging:
- Transaction timestamps (millisecond or microsecond precision)
- System logs with second-level granularity
- Performance monitoring (operations/second)
4. Telecommunications and Networking
Network synchronization:
- Cell towers synchronized to GPS time (nanosecond precision)
- Internet infrastructure timing
- 5G networks require nanosecond coordination
- Precision Time Protocol (PTP) for industrial networks
Data transmission:
- Bit rates measured in bits/second (Mbps, Gbps)
- Latency measured in milliseconds
- Packet timing and queuing
5. Navigation and GPS
Global Positioning System:
- Atomic clocks on satellites (accuracy ~10 nanoseconds)
- Signal travel time calculations
- Position accuracy requires nanosecond precision
- GNSS systems (GPS, GLONASS, Galileo, BeiDou)
Aviation:
- Aircraft navigation timing
- Air traffic control coordination
- Flight duration measurements
6. Financial and Trading
High-frequency trading:
- Microsecond timestamps on transactions
- Trading algorithms execute in microseconds
- Market data feeds timestamped to nanoseconds
- Regulatory requirements for precise time-stamping
Banking:
- Transaction timestamps
- Interest calculations (per second for some instruments)
- Automated trading systems
7. Sports and Athletics
Competition timing:
- Track and field (0.01 second precision)
- Swimming (0.01 second precision)
- Skiing, bobsled (0.01 second precision)
- Motor racing (0.001 second precision)
Training and performance:
- Stopwatches for interval training
- Heart rate monitors (beats/second)
- Pace calculations (minutes per kilometer/mile)
- Reaction time testing
8. Manufacturing and Industrial
Process control:
- Machine cycle times (seconds)
- Assembly line timing
- Quality control measurements
- Synchronization of robots and automation
Industrial timing:
- Conveyor belt speeds
- Injection molding cycle times (2-60 seconds typical)
- 3D printing layer times
- Chemical process durations
When to Use hours
and Applications
1. Time Zones and Global Coordination
The hour is the basis for global time coordination:
-
UTC (Coordinated Universal Time):
- Global time standard (replaced GMT in 1960s)
- Based on atomic clocks
- All time zones expressed as UTC offset
-
Major time zones:
- EST (Eastern Standard Time): UTC-5
- CST (Central Standard Time): UTC-6
- MST (Mountain Standard Time): UTC-7
- PST (Pacific Standard Time): UTC-8
- GMT/WET (Western European Time): UTC+0
- CET (Central European Time): UTC+1
- IST (Indian Standard Time): UTC+5:30
- JST (Japan Standard Time): UTC+9
- AEST (Australian Eastern Standard Time): UTC+10
-
Business hours across zones:
- "9 AM EST / 6 AM PST" (3-hour difference)
- International meetings: Finding overlapping work hours
- "Follow the sun" support: 24-hour coverage across global offices
-
International Date Line:
- 180° longitude (opposite side of Earth from Prime Meridian)
- Crossing eastward: Lose one day (skip 24 hours forward)
- Crossing westward: Gain one day (repeat 24 hours)
2. Scheduling and Calendar Systems
Hours are the building blocks of schedules:
-
Digital calendars:
- Google Calendar, Outlook: Default 1-hour event blocks
- Day view: Shows 24 hours (or work hours only)
- Week view: 168 hours (7 × 24)
- Buffer time: 15-30 minutes between hour blocks
-
Appointment systems:
- Medical: 15-minute to 1-hour slots
- Salon/spa: 30 minutes to 3 hours
- Professional meetings: 30-minute or 1-hour default
-
Business hours:
- Standard: 9 AM - 5 PM (8 hours, often called "9-to-5")
- Extended: 8 AM - 6 PM (10 hours)
- 24/7 operations: Open all 24 hours, 7 days per week
-
Peak hours vs. off-peak:
- Rush hour: 7-9 AM, 4-7 PM (commute times)
- Electricity pricing: Higher rates during peak demand hours
- Gym: Busiest 5-7 PM (post-work)
3. Astronomy and Earth Science
The hour reflects Earth's rotation:
-
Earth's rotation:
- 360° in ~24 hours = 15° per hour
- Solar noon: Sun crosses local meridian (highest point in sky)
- Local solar time: Based on sun position (varies with longitude)
- Mean solar time: Averaged over year (accounts for orbital eccentricity)
-
Equation of time:
- Sundial time vs. clock time can differ by ±16 minutes
- Due to Earth's elliptical orbit and axial tilt
- Clock time is averaged over the year
-
Hour angle (astronomy):
- Angular distance (in hours) from local meridian
- 1 hour = 15° of celestial sphere rotation
- Used to determine star positions for telescope pointing
-
Sidereal vs. solar day:
- Sidereal day: 23 hours 56 minutes 4 seconds (rotation relative to stars)
- Solar day: 24 hours (rotation relative to sun)
- Difference: Earth moves along orbit, sun appears to shift ~1° per day
4. Energy and Power Consumption
Energy usage measured in watt-hours:
-
Kilowatt-hour (kWh):
- Energy used by 1 kilowatt (1,000 watts) running for 1 hour
- Standard unit for electricity billing
- Average US home: 30 kWh per day (877 kWh per month)
-
Appliance energy use:
- 100W light bulb for 10 hours = 1 kWh
- Electric oven: 2-3 kWh per hour of use
- Central AC: 3-5 kWh per hour
- Laptop: 0.05 kWh per hour (50 watts)
- Refrigerator: 1-2 kWh per day (constant running)
-
Time-of-use pricing:
- On-peak hours: Higher electricity rates (typically 1-9 PM)
- Off-peak hours: Lower rates (typically 9 PM - 9 AM)
- Encourages load shifting to flatten demand curve
-
Battery capacity:
- Milliamp-hour (mAh) or watt-hour (Wh)
- Phone battery: 3,000 mAh (11 Wh) ≈ 2-3 hours screen-on time
- Laptop battery: 50-100 Wh ≈ 5-10 hours use
- Electric car: 60-100 kWh ≈ 250-400 miles range
5. Healthcare and Medicine
Medical dosing and monitoring uses hours:
-
Medication schedules:
- "Every 4 hours" = 6 times per day
- "Every 6 hours" = 4 times per day (QID: quater in die)
- "Every 8 hours" = 3 times per day (TID: ter in die)
- "Every 12 hours" = 2 times per day (BID: bis in die)
- "Every 24 hours" = 1 time per day (QD: quaque die)
-
Drug half-life:
- Time for drug concentration to decrease by half
- Acetaminophen: 2-3 hours
- Caffeine: 5-6 hours
- Alcohol: Eliminated at ~0.015% BAC per hour
-
Fasting requirements:
- Pre-surgery: 8-12 hours fasting (NPO: nil per os)
- Cholesterol test: 9-12 hours fasting
- Glucose tolerance test: 8-hour overnight fast
-
Labor and delivery:
- Labor stages measured in hours
- First stage: 6-12 hours (first baby), 4-8 hours (subsequent)
- Active labor: Cervical dilation ~1 cm per hour
- Pushing stage: 1-3 hours (first baby), 15 min-2 hours (subsequent)
-
Medical shift lengths:
- Resident work-hour restrictions: Max 80 hours per week, max 24-hour shifts
- Nurse shifts: Typically 8 or 12 hours
- Concerns about fatigue and patient safety
6. Computing and Technology
Hours measure uptime and usage:
-
Server uptime:
- "Five nines" (99.999%): 5.26 minutes downtime per year
- "Four nines" (99.99%): 52.6 minutes downtime per year
- "Three nines" (99.9%): 8.77 hours downtime per year
- Measured in hours of continuous operation
-
Data retention:
- Backup schedules: Hourly, daily, weekly
- Log rotation: Every 24 hours (daily logs)
- Cloud storage: Deleted items retained 30 days (720 hours)
-
Usage tracking:
- Screen time: Hours per day on devices
- YouTube Creator Studio: Watch hours (4,000 hours past year for monetization)
- Video games: "Hours played" stat
- Social media: "You've been using this app for 2 hours today"
-
Rendering and processing:
- Video rendering: "2 hours to render 10-minute 4K video"
- 3D modeling: "12-hour render time for scene"
- Machine learning training: "Training took 100 GPU-hours"
7. Legal and Regulatory
Many laws reference hours:
-
Work hour regulations:
- Fair Labor Standards Act (FLSA): 40-hour work week threshold
- Overtime pay: Time-and-a-half for hours beyond 40/week
- Maximum driving hours: Truckers limited to 11 hours driving per 14-hour window
-
Alcohol service hours:
- Many states prohibit alcohol sales certain hours (e.g., 2 AM - 6 AM)
- "Last call": Final hour for ordering drinks
-
Quiet hours:
- Residential noise ordinances: Often 10 PM - 7 AM
- College dorms: 11 PM - 8 AM weeknights
-
Statute of limitations:
- Measured in years, but technically hours
- Parking tickets: Often 72-hour (3-day) payment window
- Right to return/refund: 24-48 hour windows
Additional Unit Information
About Second (s)
What is the base unit of time in the SI system?
The second (s) is the base unit of time in the International System of Units (SI). It's one of the seven SI base units, alongside meter (length), kilogram (mass), ampere (current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity).
All other time units (minute, hour, day, year) are derived from the second.
Why is the second defined using atoms?
The atomic definition provides a much more stable and precise standard than relying on Earth's rotation, which fluctuates.
Problems with astronomical definition:
- Earth's rotation slows by ~2 milliseconds per century (tidal friction)
- Seasonal variations affect day length
- Unpredictable fluctuations from earthquakes, atmospheric changes
- Accuracy limited to ~1 part per million
Advantages of atomic definition:
- Fundamental constant: Caesium-133 transition frequency is a property of nature
- Reproducible: Any caesium-133 atom behaves identically
- Stable: Unaffected by external conditions (temperature, pressure)
- Precise: Modern atomic clocks accurate to 1 second in 100 million years
Result: GPS, telecommunications, science, and technology require nanosecond precision impossible with astronomical timekeeping.
How many seconds are in a minute?
There are exactly 60 seconds in 1 minute.
This derives from ancient Babylonian base-60 (sexagesimal) mathematics, which established 60 as the standard division for time over 4,000 years ago.
Conversions:
- 1 minute = 60 seconds
- 2 minutes = 120 seconds
- 5 minutes = 300 seconds
- 10 minutes = 600 seconds
How many seconds are in an hour?
There are exactly 3,600 seconds in 1 hour.
Calculation:
- 1 hour = 60 minutes
- 1 minute = 60 seconds
- 1 hour = 60 × 60 = 3,600 seconds
Conversions:
- 1 hour = 3,600 seconds
- 2 hours = 7,200 seconds
- 12 hours = 43,200 seconds
- 24 hours (1 day) = 86,400 seconds
How many seconds are in a day?
There are 86,400 seconds in 1 day (24 hours).
Calculation:
- 1 day = 24 hours
- 1 hour = 3,600 seconds
- 1 day = 24 × 3,600 = 86,400 seconds
Breakdown:
- 24 hours × 60 minutes/hour × 60 seconds/minute = 86,400 seconds
Note: This assumes a standard 24-hour day. Due to Earth's rotation irregularities, actual solar days vary by milliseconds. Leap seconds are occasionally added to keep atomic time synchronized with Earth rotation.
How many seconds are in a year?
A standard 365-day year contains 31,536,000 seconds.
Calculation:
- 365 days × 24 hours/day × 60 minutes/hour × 60 seconds/minute
- = 365 × 86,400
- = 31,536,000 seconds
Variations:
- Leap year (366 days): 31,622,400 seconds
- Julian year (365.25 days, average): 31,557,600 seconds
- Tropical year (365.2422 days, Earth orbit): 31,556,925 seconds
Fun fact: The song "Seasons of Love" from Rent states "525,600 minutes" in a year, which equals 31,536,000 seconds (365 days).
What is a millisecond?
A millisecond (ms) is one-thousandth of a second: 0.001 seconds or 10⁻³ seconds.
Conversions:
- 1 second = 1,000 milliseconds
- 1 millisecond = 0.001 seconds
- 1 minute = 60,000 milliseconds
Common uses:
- Computer response times (1-100 ms)
- Network ping times (1-300 ms typical)
- Human reaction time (~200 ms)
- Video frame duration (60 FPS = 16.67 ms/frame)
- Stopwatch hundredths (0.01 s = 10 ms)
What is a nanosecond?
A nanosecond (ns) is one-billionth of a second: 0.000000001 seconds or 10⁻⁹ seconds.
Conversions:
- 1 second = 1,000,000,000 nanoseconds (1 billion)
- 1 millisecond = 1,000,000 nanoseconds (1 million)
- 1 microsecond = 1,000 nanoseconds
Reference points:
- Light travels 30 cm (1 foot) in 1 nanosecond
- Computer processor operations: ~0.2-1 nanosecond
- GPS timing precision: ~10 nanoseconds
- RAM memory access: ~50-100 nanoseconds
Grace Hopper's demonstration: Computer pioneer Grace Hopper famously distributed 30cm lengths of wire to represent "one nanosecond" (distance light travels in 1 ns) to illustrate the importance of speed in computing.
Why are there 60 seconds in a minute instead of 100?
The 60-second minute derives from ancient Babylonian base-60 (sexagesimal) mathematics developed around 3000 BCE, over 1,000 years before the decimal system.
Reasons for base-60:
1. High divisibility: 60 has 12 divisors: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60
- Easy to divide into halves, thirds, quarters, fifths, sixths
- 100 (decimal) has only 9 divisors: 1, 2, 4, 5, 10, 20, 25, 50, 100
2. Finger counting method:
- Count 12 finger segments (phalanges) on one hand using thumb
- Track count on other hand: 12 × 5 fingers = 60
3. Astronomical convenience:
- ~360 days per year ≈ 6 × 60
- Circle divided into 360 degrees (6 × 60)
- Babylonian astronomy used these divisions
4. Historical persistence: The system spread through Egyptian, Greek, and Roman civilizations and became too entrenched to change. When mechanical clocks developed in medieval Europe, they adopted the existing Babylonian time divisions.
Attempts to decimalize time:
- French Revolutionary Calendar (1793-1805): 10-hour day, 100-minute hour, 100-second minute
- Failed: Too difficult to change clocks, conversion from traditional system
- Result: We still use Babylonian base-60 for time, but base-10 (decimal) for most other measurements
How accurate are atomic clocks?
Modern atomic clocks are extraordinarily accurate:
Caesium atomic clocks (standard):
- Accuracy: 1 second in 100 million years
- Precision: Parts per trillion (10⁻¹²)
- Used in GPS satellites, national time standards
Caesium fountain clocks (advanced):
- Accuracy: 1 second in 300 million years
- Precision: Better than 10⁻¹⁵
- Used by metrology institutes (NIST, PTB, NPL)
Optical lattice clocks (state-of-the-art):
- Accuracy: 1 second in 15-30 billion years
- Precision: 10⁻¹⁸ to 10⁻¹⁹
- Use strontium, ytterbium, or aluminum ions
- So precise they detect gravitational time dilation across centimeters of height
Comparison:
- Quartz watch: 1 second in 1-10 days (10⁻⁵ accuracy)
- Mechanical watch: 1-10 seconds per day (10⁻⁴ to 10⁻⁵)
- Sundial: Minutes per day (10⁻³)
- Atomic clock: 1 second in 100 million years (10⁻¹⁶)
Why this matters: GPS requires 10-nanosecond precision; a 1-microsecond error causes 300-meter position errors.
What are leap seconds and why do we need them?
Leap seconds are occasional one-second adjustments added to Coordinated Universal Time (UTC) to keep it synchronized with Earth's rotation.
The problem:
- Atomic time (TAI): Runs at constant rate based on caesium clocks, unchanging
- Earth rotation (UT1): Slows gradually due to tidal friction (~2 milliseconds per day longer)
- Discrepancy: Accumulates ~1 second every 18-24 months
Solution:
- Add (or theoretically remove) 1 second on June 30 or December 31
- Keeps UTC within 0.9 seconds of Earth rotation time (UT1)
- 27 leap seconds added between 1972 and 2016
- No leap seconds since 2016 (Earth rotation has been slightly faster recently)
How it works: Instead of 23:59:59 → 00:00:00, the sequence is: 23:59:59 → 23:59:60 → 00:00:00 (leap second inserted)
Controversy:
- Problems: Computer systems, GPS, networks struggle with leap seconds (software bugs, crashes)
- Proposed solution: Abolish leap seconds, let UTC and UT1 drift apart
- Debate: Ongoing since 2000s; decision may be made in 2026-2030s
Current status: Leap seconds remain in use, but their future is uncertain.
About Hour (h)
How many minutes are in an hour?
Exactly 60 minutes. This comes from the ancient Babylonian base-60 (sexagesimal) number system, which the Egyptians and Greeks adopted for dividing hours. The Latin term "pars minuta prima" (first small part) referred to the first 60-part division of an hour, giving us the modern "minute."
How many seconds are in an hour?
Exactly 3,600 seconds (60 minutes × 60 seconds).
Since 1967, when the second was redefined using atomic caesium-133 clocks, one hour equals:
- 3,600 atomic seconds
- 33,074,688,259,200,000 caesium-133 oscillations (33.07 quadrillion)
This makes the hour one of the most precisely defined units of time in existence.
How many hours are in a day?
Exactly 24 hours in one solar day.
Why 24?
- Ancient Egyptians divided day and night into 12 parts each
- 12 + 12 = 24-hour cycle
- Earth rotates 360° in 24 hours = 15° per hour
- This 15° per hour relationship forms the basis for time zones
Note: A sidereal day (rotation relative to stars) is 23 hours, 56 minutes, 4 seconds, but civil timekeeping uses the 24-hour solar day (rotation relative to the sun).
How many hours are in a year?
8,760 hours in a standard 365-day year.
Calculation: 365 days × 24 hours = 8,760 hours
For a leap year (366 days): 8,784 hours (24 more hours).
Work year: Assuming 40-hour weeks and 52 weeks, a full-time work year is 2,080 work hours (not including holidays or vacation).
Why do we use 12-hour AM/PM instead of 24-hour time?
Historical reasons:
- Ancient Egyptians and Romans divided day and night into 12 parts each
- This became culturally entrenched in English-speaking countries
- 12-hour clocks were simpler to manufacture (only need 1-12 markers)
Why 24-hour format exists:
- Eliminates AM/PM confusion (especially 12:00 AM vs. 12:00 PM)
- Preferred in military, aviation, healthcare, computing for clarity
- Standard in most non-English-speaking countries
- ISO 8601 international standard uses 24-hour format
Current usage:
- 12-hour: US, Canada, Australia, Philippines, parts of UK
- 24-hour: Most of Europe, Asia, Africa, South America, military worldwide
What's the difference between a 24-hour day and Earth's rotation?
Solar day (24 hours): Time for sun to return to same position in sky Sidereal day (23h 56m 4s): Time for Earth to rotate 360° relative to distant stars
Why the difference?
- Earth orbits the sun while rotating
- After one 360° rotation, Earth has moved ~1° along its orbit
- Must rotate an additional ~1° (4 minutes) for sun to return to same position
- 365.25 solar days per year, but 366.25 sidereal days per year (one extra rotation)
Practical impact:
- Astronomers use sidereal time for telescope pointing
- Civil timekeeping uses solar time (24-hour day)
- Stars rise ~4 minutes earlier each day (sidereal effect)
How do Daylight Saving Time changes work?
Spring forward (start of DST):
- Clocks advance 1 hour at 2:00 AM → becomes 3:00 AM
- The hour from 2:00-3:00 AM doesn't exist that day
- Day has only 23 hours
- "Lose an hour of sleep"
Fall back (end of DST):
- Clocks retreat 1 hour at 2:00 AM → becomes 1:00 AM again
- The hour from 1:00-2:00 AM occurs twice
- Day has 25 hours
- "Gain an hour of sleep"
Global variation:
- Northern Hemisphere: Starts March/April, ends October/November
- Southern Hemisphere: Starts September/October, ends March/April
- Many countries don't observe DST (China, Japan, India, most of Africa)
- Arizona and Hawaii (US states) don't observe DST
Controversy: Growing movement to abolish DST due to health impacts, minimal energy savings.
Why are time zones roughly 15 degrees wide?
Simple math:
- Earth rotates 360° in 24 hours
- 360° ÷ 24 hours = 15° per hour
- Each time zone theoretically spans 15° longitude
Reality is messier:
- Political boundaries: Zones follow country/state borders
- China uses single time zone (UTC+8) despite spanning 60° longitude (5 theoretical zones)
- India uses UTC+5:30 (half-hour offset from standard)
- Some zones are 30 or 45-minute offsets (Nepal: UTC+5:45)
Practical example:
- Greenwich, England: 0° longitude (Prime Meridian)
- Every 15° east: Add 1 hour (15°E = UTC+1, 30°E = UTC+2, etc.)
- Every 15° west: Subtract 1 hour (15°W = UTC-1, 30°W = UTC-2, etc.)
What is a "billable hour"?
A billable hour is time spent on client work that can be charged to the client, common in legal, consulting, and professional services.
How it works:
- Professionals track time in increments (often 6 minutes = 0.1 hour)
- Multiply hours by hourly rate
- Example: 7.5 billable hours × $300/hour = $2,250
Billing increment examples:
- 6 minutes = 0.1 hour (common in legal)
- 15 minutes = 0.25 hour (quarter-hour)
- Some firms round up to nearest increment
Utilization rate:
- Target: 1,500-2,000 billable hours per year (out of 2,080 work hours)
- Remaining time: Non-billable (admin, business development, training)
- 75-80% utilization considered good in many professions
Ethical concerns:
- Pressure to inflate hours
- Some professions moving to flat-fee or value-based pricing
Can an hour ever be longer or shorter than 60 minutes?
In standard timekeeping: No. An hour is always exactly 60 minutes or 3,600 seconds.
Exceptions and special cases:
-
Leap seconds:
- Very rarely, an extra second added to last minute of day
- Makes that minute 61 seconds, but hour still 3,600 seconds overall
- Last hour of day becomes 3,601 seconds
- 27 leap seconds added 1972-2016
-
Daylight Saving Time transitions:
- "Spring forward": The 2:00 AM hour is skipped (day has 23 hours)
- "Fall back": The 1:00 AM hour occurs twice (day has 25 hours)
- This affects the day length, not individual hour length
-
Historical seasonal hours:
- Ancient/medieval timekeeping used "unequal hours"
- Summer daylight hour ≈ 75 minutes
- Winter daylight hour ≈ 45 minutes
- Obsolete since mechanical clocks standardized equal hours
Future possibility:
- If leap seconds abolished, may use "leap hours" every few centuries instead
Why is rush hour called an "hour" when it lasts 2-3 hours?
Etymology: "Rush hour" originally referred to the peak single hour of commuter traffic, but the term stuck even as traffic congestion expanded.
Modern reality:
- Morning rush: 7:00-9:00 AM (2-3 hours)
- Evening rush: 4:00-7:00 PM (3-4 hours)
- Can extend longer in major cities
Related terms:
- "Peak hours": Broader term for high-traffic periods
- "Congestion pricing": Charging more during rush hours to reduce traffic
- "Off-peak": Outside rush hours, usually smoother travel
Cultural note: The term persists despite inaccuracy, similar to how we still say "dial a phone" or "roll down the window."
Conversion Table: Second to Hour
| Second (s) | Hour (h) |
|---|---|
| 0.5 | 0 |
| 1 | 0 |
| 1.5 | 0 |
| 2 | 0.001 |
| 5 | 0.001 |
| 10 | 0.003 |
| 25 | 0.007 |
| 50 | 0.014 |
| 100 | 0.028 |
| 250 | 0.069 |
| 500 | 0.139 |
| 1,000 | 0.278 |
People Also Ask
How do I convert Second to Hour?
To convert Second to Hour, enter the value in Second in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our time converter page to convert between other units in this category.
Learn more →What is the conversion factor from Second to Hour?
The conversion factor depends on the specific relationship between Second and Hour. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Hour back to Second?
Yes! You can easily convert Hour back to Second by using the swap button (⇌) in the calculator above, or by visiting our Hour to Second converter page. You can also explore other time conversions on our category page.
Learn more →What are common uses for Second and Hour?
Second and Hour are both standard units used in time measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our time converter for more conversion options.
For more time conversion questions, visit our FAQ page or explore our conversion guides.
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Other Time Units and Conversions
Explore other time units and their conversion options:
- Minute (min) • Second to Minute
- Day (d) • Second to Day
- Week (wk) • Second to Week
- Month (mo) • Second to Month
- Year (yr) • Second to Year
- Millisecond (ms) • Second to Millisecond
- Microsecond (μs) • Second to Microsecond
- Nanosecond (ns) • Second to Nanosecond
- Decade (dec) • Second to Decade
- Century (c) • Second to Century
Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — Official time standards and definitions
Bureau International des Poids et Mesures — Definition of the SI base unit for time
Last verified: December 3, 2025