Astronomical Unit to Mile Converter
Convert astronomical units to miles with our free online length converter.
Quick Answer
1 Astronomical Unit = 92957130.358705 miles
Formula: Astronomical Unit × conversion factor = Mile
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.
Astronomical Unit to Mile Calculator
How to Use the Astronomical Unit to Mile Calculator:
- Enter the value you want to convert in the 'From' field (Astronomical Unit).
- The converted value in Mile will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Length category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Astronomical Unit to Mile: Step-by-Step Guide
Converting Astronomical Unit to Mile involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Astronomical Unit = 9.2957e+7 milesExample Calculation:
Convert 10 astronomical units: 10 × 9.2957e+7 = 9.2957e+8 miles
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.
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Need to convert to other length units?
View all Length conversions →What is a Astronomical Unit and a Mile?
1 astronomical unit (AU) = 149,597,870,700 meters (EXACT)
The astronomical unit is a unit of length in astronomy and planetary science, representing the mean distance from Earth to the Sun. Since 2012, the AU has been a defined constant—exactly 149,597,870,700 m—rather than a measured quantity.
Why Not Just Use Kilometers?
Scale problem: Solar System distances in kilometers become unwieldy:
- Earth to Sun: 149,597,871 km (hard to grasp)
- Jupiter to Sun: 778,500,000 km (increasingly meaningless)
- Neptune to Sun: 4,500,000,000 km (just a big number)
AU makes it intuitive:
- Earth: 1.00 AU (baseline)
- Jupiter: 5.20 AU (5× farther than Earth)
- Neptune: 30.1 AU (30× Earth's distance)
The human brain handles ratios better than absolute numbers. "Neptune is 30 times farther from the Sun than Earth" is far more comprehensible than "Neptune is 4.5 billion kilometers from the Sun."
Light Travel Time
The AU has a natural time component:
1 AU = 8 minutes 19 seconds at the speed of light
- Light from the Sun takes 8m 19s to reach Earth
- If the Sun suddenly vanished, we wouldn't know for 8+ minutes
- Solar flares and coronal mass ejections take this long to arrive
- Real-time communication with spacecraft: Earth-Mars = 4-24 minutes one-way delay (depending on orbital positions)
AU vs. Light-Year vs. Parsec
Three different distance scales for different contexts:
| Unit | Meters | Use Case | |----------|-----------|--------------| | Astronomical Unit (AU) | 1.496 × 10¹¹ m | Solar System (planets, asteroids, comets) | | Light-year (ly) | 9.461 × 10¹⁵ m (63,241 AU) | Interstellar distances (nearest stars) | | Parsec (pc) | 3.086 × 10¹⁶ m (206,265 AU) | Galactic/extragalactic distances (parallax-based) |
Why each exists:
- AU: Human-scale for our cosmic neighborhood
- Light-year: Intuitive (distance light travels in a year)
- Parsec: Technical (distance at which 1 AU subtends 1 arcsecond)
The mile (symbol: mi or sometimes mi.) is a unit of length defined as exactly 5,280 feet, which equals 1,760 yards or 1,609.344 meters in the metric system.
Standard Mile (Statute Mile)
In the United States, the statute mile (land mile) is the standard distance measurement for:
- Road distances: "Exit 42, 3 miles"
- Speed limits: "Speed Limit 65 mph" (miles per hour)
- Vehicle odometers: Car mileage readings
- Real estate: "Located 2 miles from the beach"
- Running races: The classic mile race, 5K (3.1 miles), 10K (6.2 miles), marathon (26.2 miles)
- Property records: Land surveys, real estate listings, school district boundaries
Important Distinctions: Types of Miles
When Americans say "mile," they almost always mean the statute mile (5,280 feet). However, there are other types of miles:
1. Statute Mile (Land Mile):
- 5,280 feet or 1,609.344 meters
- Standard mile used on land for roads, running, and general measurement
- Used in US, UK (roads), Myanmar
2. Nautical Mile:
- 6,076 feet or 1,852 meters
- Used in maritime and aviation contexts
- One nautical mile = one minute of latitude on Earth (1/60th of a degree)
- Approximately 15% longer than statute mile
- Speed: measured in knots (nautical miles per hour)
3. Survey Mile (US):
- Historically used in US land surveys before 1959
- Slightly different from international mile (difference ~2 parts per million)
- 1 US survey mile = 5,280 US survey feet = 1,609.347 meters (vs. 1,609.344 international)
- Rarely encountered today outside historical property records
- Some older property boundaries still reference survey miles
Why 5,280 Feet? The Furlong Explanation
The number 5,280 seems arbitrary, but it has historical logic:
Furlong Division:
- A furlong is an old English unit = 660 feet (220 yards)
- Etymology: "furrow long"—the distance a team of oxen could plow before needing rest
- 8 furlongs = 1 mile → 8 × 660 = 5,280 feet
- Made the mile extremely practical for agricultural land measurement
Elizabethan Standardization (1593):
- Queen Elizabeth I's statute defined mile = 8 furlongs
- Reconciled competing systems:
- Agricultural furlongs (essential for land surveys)
- Traditional Roman-derived mile lengths (~5,000 feet)
- Cementing the 5,280-foot standard that persists 430+ years later
Divisibility advantages:
- 5,280 is divisible by: 1, 2, 3, 4, 5, 6, 8, 10, 11, 12, 15, 16, 20, 22, 24, 30, 32, 33, 40, 44, 48, 60, 66, 80, 88, 96, 110, 120, 132, 160, 176, 220, 240, 264, 330, 352, 440, 480, 528, 660, 880, 1056, 1320, 1760, 2640, 5280
- Makes fractions (1/2, 1/4, 1/8, 1/10 mile) easy whole numbers in feet
Note: The Astronomical Unit is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Mile belongs to the imperial/US customary system.
History of the Astronomical Unit and Mile
Ancient Underestimates (300 BCE - 1500 CE)
Aristarchus of Samos (3rd century BCE): The first known attempt to measure the Earth-Sun distance. Using lunar phases and geometry, Aristarchus estimated the Sun was 18-20 times farther than the Moon. His method was sound, but observational limitations led to severe underestimation.
Actual ratio: Sun is ~400× farther than the Moon, not 20×.
Ptolemy's geocentric model (2nd century CE): Ptolemy's Almagest placed the Sun relatively close—around 1,200 Earth radii (~7.6 million km), about 5% of the true distance. This underestimation persisted for 1,400 years during the geocentric era.
Copernican Revolution (1543-1600s)
Nicolaus Copernicus (1543): De revolutionibus orbium coelestium established the heliocentric model. While Copernicus correctly ordered the planets, his distance estimates were still too small—placing the Sun about 20 million km away (13% of the actual distance).
Johannes Kepler (1609-1619): Kepler's laws of planetary motion (published in Astronomia Nova and Harmonices Mundi) enabled calculation of relative planetary distances. If Earth's orbit is 1 AU, then:
- Venus: 0.72 AU
- Mars: 1.52 AU
- Jupiter: 5.20 AU
Problem: Kepler knew the proportions, but not the absolute scale. What was the AU in meters or kilometers?
The Transit of Venus Method (1761-1769)
Edmond Halley's proposal (1716): Halley realized that observing Venus crossing the Sun's face (a "transit") from different Earth locations would create a parallax effect, enabling triangulation of the Earth-Sun distance.
1761 Transit of Venus: International expeditions to Siberia, South Africa, India, and the South Pacific. Observations were complicated by:
- The "black drop effect" (Venus appearing to stick to the Sun's edge)
- Cloudy weather disrupting measurements
- Imprecise timekeeping
1769 Transit of Venus: More extensive global coordination:
- Captain James Cook: Observed from Tahiti (Point Venus)
- Charles Mason & Jeremiah Dixon: Observed from the Cape of Good Hope
- Russian expeditions: Observed from Siberia
Result: Combined data yielded an Earth-Sun distance of approximately 153 million km, within 2% of the modern value (150M km). This was the first accurate measurement of the AU.
Why transits work: Observers at different latitudes see Venus cross the Sun along slightly different paths. The timing difference creates a parallax angle:
tan(parallax) = (Earth baseline) / (Earth-Sun distance)
With a known Earth baseline (distance between observation sites) and measured parallax, the AU could be calculated.
19th Century Refinement (1800-1900)
1874 and 1882 Transits of Venus: Equipped with photography and telegraph time-synchronization, astronomers improved AU measurements to ~149.5 million km.
Asteroid parallax (1898-1900): The asteroid 433 Eros passes closer to Earth than Venus, providing better parallax measurements. During Eros's 1900-1901 opposition, global observatories measured its position, refining the AU to 149.53 million km (±0.03%).
Term standardization: The phrase "astronomical unit" became standard in the late 19th century, replacing earlier terms like "solar distance" or "Earth's mean distance."
20th Century Precision (1961-2012)
Radar ranging to Venus (1961): The Goldstone Observatory and Jodrell Bank transmitted radar signals to Venus and measured the round-trip time. Since radio waves travel at the speed of light (c), the distance calculation was straightforward:
Distance = (c × round-trip time) / 2
Result: The AU was refined to 149,597,870 km (±1 km precision).
Radar ranging to Mars (1965-1976): Mariner and Viking spacecraft provided radar measurements, cross-verifying the Venus-based AU.
Viking landers (1976): Precise radio tracking of the Viking landers on Mars enabled AU measurements to sub-kilometer precision.
Jet Propulsion Laboratory ephemerides: JPL's Development Ephemeris (DE) models incorporated radar, spacecraft tracking, and lunar laser ranging. By 2000, the AU was known to meter-level precision.
IAU 2012 Redefinition
The problem: The AU was previously defined as "the radius of an unperturbed circular Newtonian orbit about the Sun of a particle having infinitesimal mass, moving with a mean motion of 0.01720209895 radians per day (the Gaussian gravitational constant)."
This definition was:
- Circular (tied to a theoretical model, not measurable)
- Dependent on the solar mass (which itself was measured in AU-based units)
- Subject to revision as measurements improved
The solution (IAU Resolution B2, 2012): The International Astronomical Union redefined the AU as a fixed constant:
1 AU = 149,597,870,700 meters (EXACT)
Why this matters:
- Consistency: The AU no longer changes with better measurements of solar mass
- Spacecraft navigation: JPL's navigation software uses this exact constant
- Parallels SI units: Like the meter (defined via the speed of light), the AU is now a defined standard, not a derived quantity
Fun fact: The chosen value (149,597,870,700 m) was the best measurement available in 2012, now frozen as the definition.
Cultural and Scientific Impact
The AU represents humanity's growing comprehension of cosmic scale:
- Ancient world: Sun thought to be ~10 million km away
- Kepler era: Relative distances known, absolute scale uncertain
- 1769: First accurate measurement (153M km, 2% error)
- 1961: Radar precision (±1 km)
- 2012: Defined as exact constant (no error—it IS the standard)
This progression mirrors the scientific method: hypothesis → observation → refinement → standardization.
of the Mile
1. Roman Origins: Mille Passus (Ancient Rome, ~500 BCE - 476 CE)
The word "mile" derives from the Latin "mille passus", meaning "a thousand paces."
Roman pace (passus):
- Distance from where one foot left the ground to where the same foot landed again
- Essentially two steps (left step + right step = 1 pace)
- Approximately 5 Roman feet per pace
Roman mile:
- 1,000 paces = approximately 5,000 Roman feet
- Modern equivalent: ~4,850-5,000 modern feet (Roman foot ≈ 11.65 inches)
- Roman roads throughout empire marked with milestones (miliarium) at one-mile intervals
- Milestones showed distance to Rome ("All roads lead to Rome")
Roman road system:
- Over 250,000 miles of roads at empire's peak
- Standardized mile markers enabled trade, military logistics, taxation
- Many modern European roads follow ancient Roman routes
2. Medieval Variation (476 CE - 1593)
After the fall of the Roman Empire (476 CE), mile lengths varied dramatically across regions:
England:
- Miles ranged from 5,000 to 6,000 feet depending on region and purpose
- London mile, merchant mile, agricultural mile all differed
- Created confusion for trade, land ownership, taxation
Scotland:
- Scottish mile = approximately 5,952 feet (about 13% longer than modern statute mile)
- Remained in use until Scotland adopted English statute mile (18th century)
Ireland:
- Irish mile = approximately 6,720 feet (about 27% longer than statute mile)
- Used until Irish Free State adopted statute mile (1826)
Germanic regions:
- Various "meile" lengths: Prussian mile ~24,000 feet, Bavarian mile ~27,000 feet
- Some exceeded 4-5 modern statute miles in length
- Created massive confusion for international trade
Why such variation?
- No central authority after Rome's fall
- Local rulers set own standards
- Miles based on local geographic features (e.g., distance between towns)
- Agricultural needs varied by region (different furlong lengths)
3. 1593: Elizabethan Standardization
Queen Elizabeth I's Statute (1593):
- English Parliament passed Act during Elizabeth I's reign
- Defined statute mile as exactly 8 furlongs or 5,280 feet
- Became legal standard throughout England, Wales, later entire British Empire
Why this specific definition?
- Reconciled competing systems:
- Traditional mile lengths (Roman-derived ~5,000 feet)
- Agricultural furlongs (660 feet, critical for land surveys)
- Agricultural economy:
- England's economy heavily agricultural in 1590s
- Land measurement = taxation, property rights, inheritance
- Furlong-based system essential for open field system farming
- Mathematical convenience:
- 8 furlongs = easy subdivision (1/2 mile = 4 furlongs, 1/4 mile = 2 furlongs)
- 5,280 feet highly divisible (see "Why 5,280 Feet?" section)
Spread through British Empire:
- England → British colonies (American colonies, India, Australia, Canada, etc.)
- By 1800s, statute mile used across most English-speaking world
- Became embedded in American infrastructure during colonial period
4. 1959: International Yard and Pound Agreement
Background:
- By 1950s, slight variations existed between US and British yard/foot definitions
- Caused problems for international engineering, aviation, scientific collaboration
- Difference tiny (~2 parts per million) but mattered for precision work
Agreement (July 1, 1959):
- Participating countries: US, UK, Canada, Australia, New Zealand, South Africa
- Defined 1 yard = exactly 0.9144 meters (based on metric system)
- Automatically defined 1 foot = exactly 0.3048 meters
- 1 mile = exactly 1,609.344 meters (5,280 × 0.3048)
Impact:
- Eliminated tiny measurement variations between English-speaking countries
- Anchored imperial units to metric system for first time
- Enabled precise conversions for international trade, aviation, engineering
- US survey mile retained for legacy land surveys (pre-1959 property records)
Today:
- International mile (1,609.344 meters) universally used
- US survey mile exists only in historical documents
- Metric system standard for science; mile persists for US/UK roads
5. Modern Usage and Metrication Resistance
Countries still using miles (2025):
- United States: All road signs, speed limits, odometers in miles/mph
- United Kingdom: Road signs and speed limits in miles/mph (other measurements metric)
- Myanmar (Burma): Officially uses miles, though metric adoption increasing
Countries that switched from miles to kilometers:
- Canada: Converted 1970s (gradual process, completed by 1980)
- Australia: Converted 1970s (metric conversion 1970-1988)
- New Zealand: Converted 1970s
- Ireland: Converted 2005 (last EU country to switch road signs)
- South Africa: Converted 1970s
Why US hasn't converted:
- Infrastructure investment: Millions of road signs, billions of dollars to replace
- Vehicle fleet: 250+ million vehicles with mph speedometers
- Public resistance: Multiple metrication attempts (1970s Metric Conversion Act) failed
- Economic factors: No compelling economic advantage (US economy functions fine with miles)
- Cultural identity: Miles seen as part of American tradition
US Metric Conversion Act (1975):
- Made metric system "preferred" for US trade and commerce
- Made conversion voluntary, not mandatory
- Created US Metric Board (later disbanded)
- Resulted in "soft metrication" (2-liter soda bottles, 100m races) but not roads
Common Uses and Applications: astronomical units vs miles
Explore the typical applications for both Astronomical Unit (imperial/US) and Mile (imperial/US) to understand their common contexts.
Common Uses for astronomical units
1. Planetary Science and Orbital Mechanics
The AU is the natural unit for describing planetary orbits using Kepler's laws.
Kepler's Third Law:
P² = a³
Where:
- P = orbital period (Earth years)
- a = semi-major axis (AU)
Example: Mars
- Semi-major axis: 1.524 AU
- Predicted period: √(1.524³) = √(3.540) = 1.881 Earth years
- Actual period: 1.881 years (687 days) ✓
Why AU simplifies this: In SI units, Kepler's Third Law requires the gravitational constant G and solar mass M☉:
P² = (4π² / GM☉) × a³
Using AU and years, the constants vanish!
2. Asteroid and Comet Tracking
Orbital elements use AU:
- Semi-major axis (a): Average orbital distance (AU)
- Perihelion distance (q): Closest approach to Sun (AU)
- Aphelion distance (Q): Farthest point from Sun (AU)
Example: Halley's Comet
- Semi-major axis: 17.8 AU
- Perihelion: 0.586 AU (inside Venus's orbit)
- Aphelion: 35.1 AU (beyond Neptune)
- Orbital period: 75-76 years
Near-Earth Object (NEO) classification:
- Atens: Semi-major axis <1.0 AU, perihelion >0.983 AU
- Apollos: Semi-major axis >1.0 AU, perihelion <1.017 AU
- Amors: Semi-major axis >1.0 AU, perihelion 1.017-1.3 AU
3. Exoplanet Characterization
When astronomers discover exoplanets, they report orbital distances in AU for comparison with our Solar System.
Kepler-452b ("Earth's cousin"):
- Star: G-type (Sun-like)
- Distance from star: 1.05 AU
- Orbital period: 385 days
- Size: 1.6× Earth diameter
- In habitable zone (liquid water possible)
TRAPPIST-1 system:
- Star: Ultra-cool red dwarf (9% Sun's mass)
- 7 planets: 0.011 to 0.063 AU (all closer than Mercury!)
- 3 in habitable zone (TRAPPIST-1e, f, g)
- Why so close? Red dwarf is dim, HZ is much nearer
Proxima Centauri b:
- Distance from star: 0.0485 AU (7.3 million km)
- Orbital period: 11.2 days
- In habitable zone (red dwarf is faint)
- Nearest potentially habitable exoplanet (4.24 light-years)
4. Mission Planning and Spacecraft Navigation
Delta-v budgets: Spacecraft missions calculate fuel requirements based on AU distances.
Hohmann transfer orbit (Earth to Mars):
- Earth orbit: 1.00 AU (circular approximation)
- Mars orbit: 1.52 AU
- Transfer orbit semi-major axis: (1.00 + 1.52) / 2 = 1.26 AU
- Travel time: Half the transfer orbit period ≈ 259 days (8.5 months)
Launch windows: Earth and Mars align favorably every 26 months (synodic period). Missing a window means waiting 2+ years.
Example: Perseverance rover
- Launch: July 30, 2020
- Landing: February 18, 2021
- Distance traveled: ~480 million km (depends on orbital path, not straight-line)
5. Solar Wind and Space Weather
Heliosphere: The Sun's influence extends well beyond planetary orbits, measured in AU.
Termination shock: ~90 AU
- Solar wind slows below sound speed
- Voyager 1 crossed: 94 AU (2004)
Heliopause: ~120 AU
- Boundary where solar wind meets interstellar medium
- Voyager 1 crossed: 121 AU (2012)
Bow shock: ~150 AU
- Where interstellar medium piles up against heliosphere
Oort Cloud: 2,000-100,000 AU
- Spherical shell of icy comets surrounding Solar System
- Gravitationally bound to the Sun, but barely
6. Educational and Outreach
The AU provides an intuitive scale for teaching Solar System structure.
Scale models: If Earth = 1 cm diameter:
- Sun: 109 cm (1.09 m) diameter
- Earth-Sun distance: 117 m (1 AU scale)
- Jupiter: 11 cm diameter, 608 m from Sun
- Neptune: 4 cm diameter, 3.5 km from Sun!
The "Voyage" scale model (Washington, D.C.):
- 1:10 billion scale
- Sun (Smithsonian): 1.39 m diameter sphere
- Earth: 1.3 cm (grain of rice), 15 m away
- Pluto: 0.2 cm, 590 m away
7. Historical Astronomy
Pre-AU era challenges: Before the AU was accurately measured, astronomers knew relative planetary positions but not absolute distances.
Example: Kepler knew...
- Venus is 0.72× Earth's distance
- Mars is 1.52× Earth's distance
- Jupiter is 5.20× Earth's distance
...but NOT the actual Earth-Sun distance!
The AU filled this gap, providing the absolute scale.
When to Use miles
and Applications
1. Trip Planning and Navigation
Road trip calculations:
- Distance: "It's 450 miles to Los Angeles"
- Time estimate: 450 miles ÷ 60 mph average = 7.5 hours driving
- Fuel needed: 450 miles ÷ 25 mpg = 18 gallons
- Fuel cost: 18 gallons × $4/gallon = $72
GPS navigation:
- Displays distances in miles for US users
- "In 2.3 miles, turn right"
- "Arrive at destination in 14 miles, 18 minutes"
- Route comparison: "Route A: 45 miles, 52 min" vs. "Route B: 38 miles, 58 min (toll road)"
Range anxiety (electric vehicles):
- EV range: 250-350 miles typical
- Plan charging stops for long trips: "Supercharger 180 miles ahead"
2. Speed and Velocity Measurement
Miles per hour (mph):
- Residential: 25 mph speed limit (1 mile in 2.4 minutes)
- Highway: 65 mph (1 mile per minute approximately)
- Mental math: 60 mph = exactly 1 mile per minute
Speeding tickets:
- Fines often based on mph over limit: "15 mph over = $150 fine, 25 mph over = $300"
- Reckless driving threshold: Often 20+ mph over limit or >80 mph
Sports:
- Baseball pitch speed: 90 mph fastball
- Tennis serve: 120+ mph
- Golf ball: 170+ mph off driver
3. Fitness Tracking and Health
Daily step goals:
- 10,000 steps/day = approximately 4-5 miles walked
- Average person: 2,000-2,500 steps per mile
- Taller individuals: 1,800-2,200 steps per mile
Calorie burn (walking):
- 100 calories per mile (rule of thumb, varies by weight/pace)
- 150 lb person walking 3 mph: ~80-100 calories per mile
- Running: ~100-150 calories per mile depending on weight/pace
Fitness tracker displays:
- Daily distance: "You walked 3.2 miles today"
- Weekly total: "18.5 miles this week"
- Monthly challenges: "Walk 100 miles in September"
4. Land Measurement and Surveying
Section-township system (US land surveys):
- Section: 1 square mile = 640 acres
- Township: 36 square miles (6 miles × 6 miles grid)
- Used in most US states for property descriptions
Rural property:
- "40-acre parcel with 0.5 miles of river frontage"
- "Quarter section" = 0.25 square miles = 160 acres
Easements and rights-of-way:
- "Pipeline easement extends 5 miles across property"
- "Utility right-of-way 20 feet wide, 2 miles long"
5. Emergency Services and Safety
911 response zones:
- Fire stations: Typically serve 5-10 mile radius
- Ambulance response: Target <8 minutes = ~3-4 mile radius at urban speeds
- Police patrols: Beat areas often 5-15 square miles
Evacuation orders:
- Mandatory evacuation: "All residents within 5 miles of refinery must evacuate"
- Wildfire evacuations: "Residents within 10 miles ordered to leave"
Warning systems:
- Tornado warning: Typically covers 5-10 mile path
- Flash flood warning: Watershed areas (drainage basins, measured in square miles)
6. Business and Commerce
Delivery radius:
- Food delivery: Typically 3-5 mile radius from restaurant
- Same-day delivery: Amazon, Walmart often 10-20 mile radius from fulfillment center
- Service area: Plumbers, electricians often advertise "20-mile service radius"
Trade area analysis:
- Primary trade area: 1-3 miles (70-80% of customers)
- Secondary trade area: 3-7 miles (15-20% of customers)
- Tertiary trade area: >7 miles (5-10% of customers)
Franchise territories:
- Fast food franchises: Often granted 3-5 mile exclusive territory
7. Military and Defense
Weapons ranges:
- Small arms: <1 mile effective range
- Artillery: 10-30 miles depending on system
- Cruise missiles: 1,000+ miles
Territorial waters:
- Territorial sea: 12 nautical miles from coastline (13.8 statute miles)
- Contiguous zone: 24 nautical miles (27.6 statute miles)
- Exclusive Economic Zone (EEZ): 200 nautical miles (230 statute miles)
Additional Unit Information
About Astronomical Unit (AU)
1. Why use Astronomical Units instead of kilometers or miles?
Convenience and intuition.
Solar System distances in kilometers are unwieldy:
- Jupiter: 778,500,000 km from the Sun
- Neptune: 4,500,000,000 km
In AU:
- Jupiter: 5.20 AU
- Neptune: 30.1 AU
Human brains handle ratios better than large numbers. "Neptune is 30× farther from the Sun than Earth" is far more intuitive than "Neptune is 4.5 billion kilometers away."
Scientific advantage: Kepler's Third Law simplifies to P² = a³ when using AU and years, eliminating gravitational constants.
2. How many kilometers/miles is 1 AU?
Exactly 149,597,870.700 kilometers (since 2012 IAU definition).
Rounded values:
- Metric: ~150 million km (1.496 × 10⁸ km)
- Imperial: ~93 million miles (9.296 × 10⁷ mi)
Why "exactly"? As of 2012, the AU is a defined constant (like the speed of light), not a measured quantity. The meter is defined via the speed of light, and the AU is defined in meters, making it exact.
3. How long does it take light to travel 1 AU?
499.0 seconds = 8 minutes 19 seconds.
This is the "light travel time" from the Sun to Earth. When you see the Sun in the sky, you're seeing it as it was 8 minutes 19 seconds ago.
Implications:
- Solar flares take 8m 19s to reach Earth
- If the Sun vanished, we wouldn't know for 8+ minutes
- Real-time communication with Mars: 4-24 minute one-way delay
Formula:
Time = distance / speed of light
Time = 149,597,870,700 m / 299,792,458 m/s = 499.0 seconds
4. What is the difference between AU, light-year, and parsec?
Three distance units for different scales:
| Unit | Definition | Meters | Use Case | |----------|---------------|-----------|--------------| | AU | Earth-Sun distance | 1.496 × 10¹¹ m | Solar System (planets, asteroids) | | Light-year | Distance light travels in 1 year | 9.461 × 10¹⁵ m | Interstellar (nearest stars) | | Parsec | Distance where 1 AU subtends 1 arcsec | 3.086 × 10¹⁶ m | Galactic/extragalactic |
Conversions:
- 1 light-year = 63,241 AU
- 1 parsec = 206,265 AU = 3.26 light-years
Why each exists:
- AU: Intuitive for our cosmic neighborhood
- Light-year: Public-friendly (distance light travels in a year)
- Parsec: Technical (based on parallax measurements)
5. Why was the AU redefined in 2012?
To eliminate circular dependencies and fix the AU as a constant.
Old definition (pre-2012): The AU was tied to the Gaussian gravitational constant and solar mass, creating circular logic:
- Solar mass measured in kg using AU-based planetary orbits
- AU defined using solar mass
- Improved measurements of one changed the other
New definition (IAU 2012): 1 AU = 149,597,870,700 meters (EXACT)
Benefits:
- Consistency: The AU never changes, even with better solar mass measurements
- Spacecraft navigation: JPL navigation software uses this exact constant
- Parallels SI system: Like the meter (defined via speed of light), AU is now a defined standard
Fun fact: The chosen value was the best 2012 measurement, now frozen as the definition.
6. How far has Voyager 1 traveled in AU?
164 AU as of 2024 (24.5 billion km from the Sun).
Journey milestones:
- 1977: Launch from Earth (1 AU)
- 1979: Jupiter flyby (5.2 AU)
- 1980: Saturn flyby (9.5 AU)
- 2004: Crossed termination shock (94 AU) — solar wind slowed
- 2012: Entered interstellar space (121 AU) — crossed heliopause
- 2024: 164 AU and counting
Speed: 3.6 AU/year (17 km/s relative to the Sun)
Perspective:
- Voyager 1 has traveled 164× the Earth-Sun distance
- It's traveled only 0.0026 light-years (0.26% of a light-year)
- At this speed, it would take 75,000 years to reach Proxima Centauri (4.24 light-years)
7. What is the habitable zone in AU for our Solar System?
Approximately 0.95 to 1.37 AU for a Sun-like star.
Inner edge (0.95 AU): Too close → runaway greenhouse effect (like Venus at 0.72 AU)
- Water vapor traps heat
- Surface water evaporates
- Planet becomes uninhabitable
Outer edge (1.37 AU): Too far → frozen surface (Mars at 1.52 AU is marginal)
- Insufficient sunlight to maintain liquid water
- CO₂ freezes, reducing greenhouse warming
Earth (1.00 AU): Perfect!
- Liquid water oceans
- Temperate climate (greenhouse effect keeps average ~15°C)
Mars (1.52 AU): Marginal
- Thin atmosphere (lost over billions of years)
- Surface water frozen, but subsurface ice exists
- Past liquid water evidence (ancient river valleys)
Note: Habitable zone width depends on star type:
- Red dwarfs (dim): HZ is 0.05-0.15 AU
- Sun-like stars: HZ is 0.95-1.37 AU
- Blue giants: HZ is 10+ AU (but these stars don't live long enough for life to evolve)
8. How accurate is the AU measurement?
Perfectly accurate since 2012—it's a defined constant.
Pre-2012: The AU was measured using radar ranging, spacecraft tracking, and orbital mechanics. By 2000, precision reached sub-meter levels.
Post-2012: The IAU defined the AU as exactly 149,597,870,700 meters. This isn't a "measurement" anymore—it's the standard, like the meter is defined via the speed of light.
What this means:
- The AU has zero uncertainty (it's exact by definition)
- Measurements of planetary distances are now in meters, not AU
- The AU is a conversion factor (like 12 inches = 1 foot, exact)
9. Can you see 1 AU with the naked eye?
Yes! You're seeing across 1 AU whenever you look at the Sun.
What you're seeing:
- The Sun's surface is 1 AU away
- Sunlight takes 8 minutes 19 seconds to reach your eyes
- You're seeing the Sun as it was 8+ minutes ago
Other 1 AU experiences:
- Solar eclipses: Moon passes between Earth and Sun (~1 AU alignment)
- Sunlight warmth: Solar energy intensity at 1 AU is 1,361 W/m² (solar constant)
- Seasonal changes: Earth's 1 AU orbit, tilted 23.5°, creates seasons
10. How do astronomers measure AU distances?
Historically: Parallax, transits, and radar ranging. Now: The AU is a defined constant (not measured).
Historical methods:
1. Transits of Venus (1769): Observing Venus cross the Sun's face from different Earth locations enabled triangulation:
- Parallax angle measured
- Earth-Sun distance calculated: ~153 million km (2% error)
2. Radar ranging (1961+): Transmit radar to Venus/Mars, measure round-trip time:
Distance = (speed of light × round-trip time) / 2
Accuracy: Sub-kilometer precision
3. Spacecraft tracking (1976+): Viking landers on Mars, Voyager flybys, etc., provided precise radio ranging data.
Modern (2012+): The AU is defined as exactly 149,597,870,700 meters. Planetary distances are now measured in meters using spacecraft telemetry, and converted to AU using this exact constant.
11. Why don't we use AU for measuring distances to stars?
Because AU numbers become unwieldy for interstellar distances.
Example: Proxima Centauri (nearest star)
- Distance: 268,000 AU
- In light-years: 4.24 ly (much cleaner!)
It's like measuring New York to Tokyo in millimeters:
- 11 trillion millimeters (accurate but awkward)
- 11,000 kilometers (appropriate scale)
Astronomers do use AU for...
- Stellar parallax calculations (1 AU baseline enables distance measurements)
- Comparing exoplanet orbits to our Solar System
But for stellar distances:
- Light-years: Public-friendly, intuitive
- Parsecs: Professional astronomy (1 pc = 206,265 AU)
12. What is beyond 100 AU?
The edge of the Solar System and the beginning of interstellar space.
50-100 AU: Kuiper Belt
- Icy objects, dwarf planets (Pluto at 39.5 AU)
- Short-period comets originate here
90 AU: Termination Shock
- Solar wind slows below sound speed
120 AU: Heliopause
- Boundary where solar wind meets interstellar medium
- Voyager 1 crossed in 2012 (121 AU)
2,000-100,000 AU: Oort Cloud
- Spherical shell of icy comets
- Gravitationally bound to the Sun
- Long-period comets originate here
125,000 AU (~2 light-years): Sun's gravitational dominance ends
- Beyond this, nearby stars' gravity is comparable
- Practical edge of the Solar System
Perspective: Even at 100 AU, you're still deep within the Sun's influence. Interstellar space (between stars) begins around 100,000 AU.
Conversion Table: Astronomical Unit to Mile
| Astronomical Unit (AU) | Mile (mi) |
|---|---|
| 0.5 | 46,478,565.179 |
| 1 | 92,957,130.359 |
| 1.5 | 139,435,695.538 |
| 2 | 185,914,260.717 |
| 5 | 464,785,651.794 |
| 10 | 929,571,303.587 |
| 25 | 2,323,928,258.968 |
| 50 | 4,647,856,517.935 |
| 100 | 9,295,713,035.871 |
| 250 | 23,239,282,589.676 |
| 500 | 46,478,565,179.353 |
| 1,000 | 92,957,130,358.705 |
People Also Ask
How do I convert Astronomical Unit to Mile?
To convert Astronomical Unit to Mile, enter the value in Astronomical Unit in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our length converter page to convert between other units in this category.
Learn more →What is the conversion factor from Astronomical Unit to Mile?
The conversion factor depends on the specific relationship between Astronomical Unit and Mile. 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 Mile back to Astronomical Unit?
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Learn more →What are common uses for Astronomical Unit and Mile?
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Last verified: December 3, 2025