Celsius to Fahrenheit Converter
Convert degrees Celsius to degrees Fahrenheit with our free online temperature converter.
Quick Answer
1 Celsius = 33.8 degrees Fahrenheit
Formula: Celsius × conversion factor = Fahrenheit
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.
Celsius to Fahrenheit Calculator
How to Use the Celsius to Fahrenheit Calculator:
- Enter the value you want to convert in the 'From' field (Celsius).
- The converted value in Fahrenheit will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Temperature category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Celsius to Fahrenheit: Step-by-Step Guide
Temperature conversions like Celsius to Fahrenheit use specific non-linear formulas.
Formula:
°F = (°C × 9/5) + 32Example Calculation:
Convert 10°C: (10 × 9/5) + 32 = 50.0°F
Common Conversion Scenarios:
- Water Freezing Point: Water freezes at 0°C, which is 32°F.
- Room Temperature: A comfortable 22°C is 71.6°F.
- Body Temperature: Normal body temperature of 37°C is 98.6°F.
- Water Boiling Point: Water boils at 100°C, which is 212°F.
- Oven Temperature: Baking at 180°C is 356°F.
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.
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View all Temperature conversions →What is a Celsius and a Fahrenheit?
What Is Celsius?
Degree Celsius (°C) is a unit of temperature on the Celsius scale, a temperature scale originally named "Centigrade" and renamed to honor Swedish astronomer Anders Celsius. It is the most common temperature scale used worldwide, adopted by virtually every country for everyday measurements and scientific work.
The Celsius scale is defined by two fixed points:
- 0°C: The freezing point of water at standard atmospheric pressure (1 atmosphere)
- 100°C: The boiling point of water at standard atmospheric pressure
The scale is divided into 100 equal intervals between these two points, making it a decimal-based (base-10) system that aligns perfectly with the metric system.
Modern scientific definition: Since 1954, Celsius has been defined relative to the Kelvin scale (the SI base unit for temperature):
- °C = K − 273.15
- K = °C + 273.15
This means a change of 1°C equals exactly a change of 1 K, but the zero points differ by 273.15 degrees.
Celsius vs. Other Temperature Scales
Celsius vs. Fahrenheit:
- Celsius: 0°C freezing, 100°C boiling (100-degree range)
- Fahrenheit: 32°F freezing, 212°F boiling (180-degree range)
- Conversion: °F = (°C × 9/5) + 32
- Use: Celsius used globally except US; Fahrenheit used primarily in US
Celsius vs. Kelvin:
- Celsius: Relative scale, can be negative, 0°C = freezing
- Kelvin: Absolute scale, no negative values, 0 K = absolute zero (-273.15°C)
- Conversion: K = °C + 273.15
- Use: Kelvin used in scientific contexts; Celsius for practical applications
Why Celsius is intuitive: The reference points (0°C and 100°C) are based on water phase transitions, which are fundamental to everyday life:
- Below 0°C: Water is solid (ice)
- 0°C to 100°C: Water is liquid
- Above 100°C: Water is gas (steam)
This makes Celsius immediately relatable—anyone who has seen ice melt or water boil understands these reference points.
Degree Fahrenheit (symbol: °F) is a unit of temperature on the Fahrenheit scale, developed by physicist Daniel Gabriel Fahrenheit in 1724. It is one of the most commonly used temperature scales in the United States.
Key reference points:
- Water freezing point: 32°F (at standard atmospheric pressure)
- Water boiling point: 212°F (at standard atmospheric pressure)
- Degree span: 180°F between freezing and boiling (212 - 32 = 180)
- Absolute zero: -459.67°F (theoretical lowest temperature)
Conversion formulas:
- To Celsius: °C = (°F - 32) × 5/9 - Convert F to C
- To Kelvin: K = (°F - 32) × 5/9 + 273.15 - Convert F to K
- From Celsius: °F = (°C × 9/5) + 32 - Convert C to F
Common temperature ranges:
- Below 0°F: Extremely cold
- 0-32°F: Very cold (below freezing)
- 32-50°F: Cold
- 50-65°F: Cool
- 65-75°F: Comfortable/room temperature
- 75-85°F: Warm
- 85-95°F: Hot
- Above 95°F: Very hot
Note: The degree symbol (°) is always used with Fahrenheit. Write "32°F" not "32F" or "32 degrees F."
Convert between temperature units: Fahrenheit converter
Note: The Celsius is part of the metric (SI) system, primarily used globally in science and trade. The Fahrenheit belongs to the imperial/US customary system.
History of the Celsius and Fahrenheit
Anders Celsius and the Original Scale (1742)
In 1742, Swedish astronomer Anders Celsius (1701–1744) proposed a temperature scale based on two fixed points related to water. However, his original scale was inverted from what we use today:
Celsius's original scale (1742):
- 0°: Boiling point of water
- 100°: Freezing point of water
This counterintuitive arrangement had water freezing at the higher number and boiling at the lower number. Celsius chose this orientation possibly because he was primarily interested in measuring cold temperatures in Sweden, making it convenient to have larger numbers for colder conditions.
Why inversion? Some historians believe Celsius wanted to avoid negative numbers when measuring cold Swedish winters. By setting freezing at 100°, he could measure winter temperatures as positive values above 100.
The Reversal: Modern Celsius Scale
Shortly after Celsius's death in 1744, the scale was reversed to its current form, where:
- 0°: Freezing point of water
- 100°: Boiling point of water
Who reversed it? Historical records are unclear, but credit is typically given to one or both:
- Carl Linnaeus (1707–1778): Swedish botanist who worked at Uppsala University with Celsius
- Jean-Pierre Christin (1683–1755): French physicist who independently proposed a similar reversed scale in 1743
The reversed scale proved more intuitive—negative numbers represent below-freezing temperatures, and positive numbers represent above-freezing, aligning with everyday experience.
From "Centigrade" to "Celsius" (1948)
For over 200 years, the scale was commonly known as "Centigrade," from the Latin words:
- "Centi": hundred
- "Grade": steps or degrees
The name described the scale's defining characteristic: 100 equal intervals between freezing and boiling.
The 1948 name change: In 1948, the 9th General Conference on Weights and Measures (CGPM) officially renamed the scale from "Centigrade" to "Celsius" for two important reasons:
- Honor Anders Celsius: Recognize the inventor's contribution to science
- Avoid confusion: The term "centigrade" was also used in French and Spanish to describe angular measurements (1/100th of a right angle), creating potential confusion in scientific contexts
The renaming standardized international terminology, making "Celsius" the official name in all languages and scientific literature.
Adoption into the Metric System (SI)
1954 - SI Integration: The 10th General Conference on Weights and Measures formally adopted Celsius into the International System of Units (SI) in 1954. Celsius was defined relative to the Kelvin scale:
- Kelvin: SI base unit for thermodynamic temperature
- Celsius: Derived unit, defined as K − 273.15
This integration meant Celsius became part of the coherent system of metric units used worldwide for science, engineering, and commerce.
1967-1968 - Definition refinement: The definition was refined to be based on the triple point of water (0.01°C, 273.16 K) rather than ice point and boiling point, providing a more precise scientific standard.
2019 - Modern definition: Following the 2019 redefinition of SI base units, the Kelvin (and thus Celsius) is now defined by fixing the Boltzmann constant, providing an even more fundamental and reproducible definition.
Global Adoption (20th Century)
Throughout the 20th century, Celsius adoption spread globally as countries adopted the metric system:
Early adopters (1790s-1800s):
- France and other European countries adopting metric system
- Gradual spread through scientific community
Mid-20th century (1960s-1980s):
- United Kingdom transitioned from Fahrenheit to Celsius (1960s-1970s)
- Canada adopted Celsius in 1975
- Australia, New Zealand adopted metric/Celsius (1960s-1970s)
- Most former British colonies transitioned to Celsius
Modern status:
- 190+ countries use Celsius as the official temperature scale
- 3 countries primarily use Fahrenheit: United States, Bahamas, Cayman Islands
- Universal in international aviation, shipping, science, and medicine
The US Exception
The United States remains the primary holdout, continuing to use Fahrenheit for:
- Weather forecasts
- Household thermostats
- Cooking temperatures (ovens, recipes)
- Public discourse
However, Celsius is used in US contexts:
- Scientific research (NASA, universities)
- Military
- Medical (increasingly, alongside Fahrenheit)
- International trade and diplomacy
Multiple attempts to convert the US to metric/Celsius (notably in the 1970s) have failed due to cultural resistance, conversion costs, and lack of political will.
-
Daniel Gabriel Fahrenheit (1686-1736): A Polish-German physicist and instrument maker who invented the mercury thermometer and developed the Fahrenheit temperature scale.
-
Early Development (1724): Fahrenheit proposed his temperature scale with three reference points:
- 0°F: Temperature of a brine solution (mixture of ice, water, and ammonium chloride salt) - the coldest temperature he could reliably reproduce in his laboratory
- 32°F: Freezing point of water (later standardized)
- 96°F: Human body temperature (later adjusted to 98.6°F)
-
Original Rationale: Fahrenheit chose these points to:
- Avoid negative numbers in normal weather (unlike earlier scales)
- Create finer graduations for better precision (180 degrees between freezing and boiling vs 100 in Celsius)
- Use easily reproducible reference points with 18th-century technology
-
Refinements (1750s onward): The scale was gradually standardized:
- Water's freezing point: exactly 32°F
- Water's boiling point: exactly 212°F (at standard atmospheric pressure)
- This created 180 degrees between the two points
- Human body temperature was remeasured at 98.6°F (not 96°F)
-
Rapid Adoption (1700s-1800s): The Fahrenheit scale quickly became popular:
- Adopted throughout the British Empire
- Standard in English-speaking countries
- Used in scientific work until the late 19th century
- Mercury thermometers using Fahrenheit became widespread
-
Celsius Competition (1742): Anders Celsius proposed the centigrade scale (later renamed Celsius) with 0° at water freezing and 100° at boiling. Simpler, but both scales coexisted.
-
Metric Movement (1900s): As the metric system spread globally:
- Most countries switched from Fahrenheit to Celsius
- Scientific community adopted Celsius/Kelvin
- UK officially switched to Celsius in the 1960s-1970s
- Canada switched to Celsius in the 1970s
-
United States Today: The US remains the only major country using Fahrenheit for everyday temperatures:
- Weather forecasts in °F
- Thermostats and home heating/cooling in °F
- Cooking temperatures in °F
- Medical thermometers in °F (though hospitals also use Celsius)
- Scientific and medical research uses Celsius/Kelvin
-
Why the US Kept Fahrenheit:
- Deeply ingrained in culture and infrastructure
- Costly to replace all thermostats, ovens, signs
- Public resistance to metric conversion
- Fahrenheit provides finer resolution for weather (1°F = 0.56°C)
-
Global Usage Today:
- Primary users: United States, some Caribbean nations (Bahamas, Belize, Cayman Islands), Palau, Federated States of Micronesia, Marshall Islands
- Former users: UK, Canada, Australia (all switched to Celsius)
- Rest of world: Uses Celsius exclusively
-
Cultural Impact: Fahrenheit remains a distinctive American characteristic, like miles and pounds, symbolizing resistance to metric adoption.
Historical Anecdote: The Case of the Missing 2.6 Degrees
Why did the body temperature change from Fahrenheit's original 96°F to the modern 98.6°F?
- Measurement Error: Early 18th-century thermometers were not yet standardized.
- The Brine Mystery: Fahrenheit used the freezing point of brine for 0°F, but the concentration of ammonium chloride and ice varies.
- Wunderlich's Research: In 1851, German physician Carl Reinhold August Wunderlich measured the temperatures of 25,000 patients and established the "new" average of 37°C, which was converted to 98.6°F.
Fahrenheit in Science Fiction: The Branding of Heat
The Fahrenheit scale has entered popular culture as a symbol of intense heat. Ray Bradbury's novel Fahrenheit 451 refers to the temperature at which book paper catches fire and burns. While scientists argue that the actual ignition temperature of paper varies with the type of paper and the oxygen levels, "451°F" has become an iconic cultural reference for censorship and destruction.
Common Uses and Applications: degrees Celsius vs degrees Fahrenheit
Explore the typical applications for both Celsius (metric) and Fahrenheit (imperial/US) to understand their common contexts.
Common Uses for degrees Celsius
The Celsius scale is the standard temperature measurement in nearly all countries except the United States, and is used extensively across all fields:
1. Weather and Meteorology
The primary temperature scale for weather forecasts, climate data, and meteorological reports worldwide. All international weather organizations use Celsius as the standard.
Weather reporting:
- Daily forecasts (high/low temperatures)
- Heat warnings (above 30-35°C)
- Freeze warnings (below 0°C)
- Wind chill calculations
- Heat index calculations
Climate science:
- Historical temperature records
- Climate change monitoring
- Sea surface temperature measurements
- Atmospheric temperature profiles
- Glacial and polar ice monitoring
Common Conversions:
- Celsius to Fahrenheit (for US weather reports)
- Celsius to Kelvin (for scientific weather data)
2. Domestic and Everyday Use
Daily temperature measurements including thermostats, air conditioning units, water heaters, and personal thermometers in all metric countries.
Household applications:
- Home heating thermostat settings (18-22°C)
- Air conditioning settings (22-24°C)
- Water heater temperature (50-60°C)
- Refrigerator temperature (4°C)
- Freezer temperature (-18°C)
- Baby bath water (37°C)
- Laundry water temperatures (cold, 30°C, 40°C, 60°C, 90°C)
3. Science and Research
Universal standard in scientific research alongside Kelvin. Used in chemistry, biology, physics, earth sciences, and engineering for temperature measurements and calculations.
Why Scientists Use Celsius:
- Easy conversion to Kelvin (K = °C + 273.15)
- Intuitive water-based reference points
- Decimal-based like other SI units
- International standardization
- Direct relationship to Kelvin (1°C = 1 K difference)
Scientific applications:
- Chemical reactions and kinetics
- Material testing and properties
- Biological experiments and incubation
- Environmental monitoring
- Quality control testing
4. Medical and Healthcare
Standard for body temperature measurements, medical equipment calibration, pharmaceutical storage requirements, and clinical guidelines worldwide.
Medical Temperature Guidelines:
- Normal body temperature: 36.5-37.5°C
- Fever threshold: Above 38°C
- Hypothermia risk: Below 35°C
- Hyperthermia emergency: Above 40°C
- Vaccine storage: 2-8°C (refrigerated) or -20°C (frozen)
Medical equipment:
- Digital thermometers
- Incubators and warmers
- Sterilization equipment (autoclaves at 121°C or 134°C)
- Laboratory analyzers
- Blood storage (4°C for whole blood, -80°C for plasma)
Convert medical temperatures with our temperature converter.
5. Culinary and Food Safety
Used for cooking instructions, food storage, and safety guidelines in most countries. Recipe books, ovens, and cooking appliances display temperatures in Celsius.
Food Safety Temperatures:
- Danger zone: 5-60°C (41-140°F) - bacteria multiply rapidly
- Refrigeration: 0-4°C (32-39°F)
- Freezing: -18°C (0°F) or below
- Safe minimum cooking: 75°C (167°F) for most foods
- Poultry: 75°C (167°F) internal temperature
- Ground meat: 71°C (160°F) internal temperature
Common Oven Settings:
- Slow/Low: 120-150°C (248-302°F)
- Moderate: 160-180°C (320-356°F)
- Standard: 180-200°C (356-392°F)
- Hot: 200-230°C (392-446°F)
- Very Hot: 230-250°C (446-482°F)
Use our Celsius to Fahrenheit converter for recipe conversions.
6. HVAC and Climate Control
Standard unit for heating, ventilation, and air conditioning systems in commercial and residential buildings worldwide.
Climate control:
- Programmable thermostats
- Central heating systems
- Air conditioning units
- Heat pumps
- Industrial climate control
- Data center cooling
7. Education
Taught as the primary temperature scale in schools worldwide as part of the metric system curriculum.
Educational contexts:
- Elementary science (water freezing/boiling)
- Chemistry (reaction temperatures)
- Physics (thermodynamics)
- Biology (optimal growth temperatures)
- Geography (climate zones)
8. Aviation and Transportation
International aviation uses Celsius for temperature reporting, along with other metric units.
Aviation applications:
- Outside air temperature (OAT)
- Engine temperature monitoring
- Cargo hold temperature
- De-icing temperature thresholds
- Weather reporting at airports (METAR/TAF)
9. Agriculture and Horticulture
Plant growth:
- Optimal growing temperatures (species-specific)
- Germination temperatures
- Greenhouse climate control
- Frost protection thresholds (below 0°C)
Livestock:
- Barn and shelter temperature monitoring
- Incubation temperatures (poultry)
- Heat stress thresholds
When to Use degrees Fahrenheit
Fahrenheit is the standard temperature scale for daily life in the United States:
Weather Reporting
Primary temperature scale for weather forecasts and reporting in the United States and its territories.
Weather applications:
- Daily temperature forecasts (high/low)
- Current temperature readings
- Heat index calculations
- Wind chill factor
- Severe weather alerts (heat advisories, freeze warnings)
- Historical climate data
- Weather maps and graphics
Why Fahrenheit in weather:
- Finer resolution (1°F increments vs 1°C)
- Human comfort range (0-100°F covers most livable temps)
- Cultural familiarity in the US
- All infrastructure uses Fahrenheit
Convert for international weather: Fahrenheit to Celsius
Home Heating and Cooling
Standard for thermostats, HVAC systems, and climate control in American homes and buildings.
HVAC uses:
- Thermostat settings (heat/cool)
- Programmable temperature schedules
- Smart home temperature control
- Zone heating/cooling
- Energy efficiency monitoring
- Comfort optimization
Typical settings:
- Winter: 68-70°F daytime, 65°F night
- Summer: 75-78°F when home, 82-85°F when away
- Energy saving: Adjust 7-10°F from comfort level when absent
Cooking and Food Preparation
Universal standard for oven temperatures, cooking instructions, and food safety in American kitchens.
Cooking applications:
- Oven temperature settings
- Recipe instructions
- Meat thermometer readings
- Food safety guidelines
- Candy/deep-fry thermometers
- Sous vide cooking
Why Fahrenheit in cooking:
- All US recipes use °F
- All ovens manufactured for US in °F
- Food safety standards in °F
- Cookbooks and packaging use °F
Medical Temperature
Standard for body temperature measurement in US healthcare and home use.
Medical uses:
- Fever detection and monitoring
- Patient vital signs
- Hypothermia/hyperthermia diagnosis
- Pediatric care (baby temperature)
- Home health monitoring
- Medical charts and records
Key thresholds:
- Normal: 98.6°F (97-99°F range)
- Fever: Above 100.4°F
- High fever: Above 103°F
- Hypothermia: Below 95°F
Note: US hospitals often use both Fahrenheit and Celsius for international standardization.
Swimming Pools and Spas
Standard for pool heating, hot tubs, and aquatic facilities in the US.
Pool/spa uses:
- Pool heater settings
- Spa/hot tub temperature
- Chemical effectiveness (temperature-dependent)
- Comfort optimization
- Energy cost management
Standard temperatures:
- Swimming pool: 78-82°F
- Competitive swimming: 77-82°F
- Hot tub: 100-104°F (max 104°F)
- Therapy pool: 92-98°F
Automotive
Used for engine monitoring and climate control in US vehicles.
Automotive uses:
- Engine temperature gauge
- Coolant temperature warning
- Cabin climate control
- Outside temperature display
- Oil temperature monitoring
Everyday Decisions
Influences daily choices in clothing, activities, and comfort throughout the US.
Daily decisions based on temperature:
- What to wear (shorts vs jacket)
- Indoor/outdoor activities
- Exercise safety
- Pet care (walk dog or not)
- Home comfort adjustments
Use our Fahrenheit converter for everyday conversions.
Additional Unit Information
About Celsius (°C)
Is Celsius the same as Centigrade?
Yes, 'Celsius' and 'Centigrade' refer to the same temperature scale.
History of the name:
- 1742-1948: Called "Centigrade" (from Latin: "centum" = hundred, "gradus" = steps)
- 1948: Officially renamed "Celsius" by the 9th General Conference on Weights and Measures
Reasons for the change:
- Honor Anders Celsius: Recognize the inventor's contribution
- Avoid confusion: "Centigrade" was also used for angular measurements (1/100th of a right angle), causing confusion in French and Spanish scientific literature
Modern usage: "Celsius" is the official and preferred term worldwide, though "Centigrade" is still occasionally heard, especially among older generations.
How does Celsius relate to Kelvin?
The Celsius scale is defined relative to the Kelvin scale, the SI base unit for thermodynamic temperature.
Key relationships:
- K = °C + 273.15 (Celsius to Kelvin)
- °C = K − 273.15 (Kelvin to Celsius)
- 1°C change = 1 K change (same interval size)
Differences:
- Zero points differ: 0°C = 273.15 K
- Kelvin is absolute: No negative values (0 K = absolute zero)
- Celsius is relative: Can be negative (negative values are below water's freezing point)
When to use which:
- Kelvin: Thermodynamics, gas laws, absolute temperature calculations
- Celsius: Everyday measurements, weather, cooking, most practical applications
Use our Celsius to Kelvin converter for instant conversions.
Why is Celsius used so widely?
Celsius is the global standard for several compelling reasons:
1. Intuitive reference points:
- 0°C = water freezes (ice formation)
- 100°C = water boils (steam formation)
- Water is fundamental to life, making these points universally relatable
2. Metric system integration:
- Decimal-based (base-10), like all metric units
- Easy to work with: 100 equal intervals
- Aligns with other SI units
3. Scientific convenience:
- Direct conversion to Kelvin (K = °C + 273.15)
- Same interval size as Kelvin (1°C = 1 K difference)
- International scientific standard
4. Global adoption:
- 190+ countries use Celsius officially
- International weather reporting
- Universal aviation standard
- Medical and healthcare standard
5. Simplicity:
- Negative temperatures = below freezing
- Positive temperatures = above freezing
- Easy to understand and remember
How do you convert Celsius to Fahrenheit quickly?
Quick mental math approximation:
- Multiply by 2
- Add 30
Examples:
- 20°C → (20 × 2) + 30 = 70°F (actual: 68°F, close!)
- 25°C → (25 × 2) + 30 = 80°F (actual: 77°F)
- 10°C → (10 × 2) + 30 = 50°F (actual: 50°F, exact!)
- 0°C → (0 × 2) + 30 = 30°F (actual: 32°F, within 2°)
Accuracy: Within 2-4°F for most common temperatures (0-30°C range)
For exact conversions:
- Formula: °F = (°C × 9/5) + 32
- Tool: Celsius to Fahrenheit converter
Memorize key points:
- 0°C = 32°F (freezing)
- 10°C = 50°F
- 20°C = 68°F
- 30°C = 86°F
- 37°C ≈ 98.6°F (body temperature)
What is a comfortable room temperature in Celsius?
Standard comfortable room temperature: 20-22°C (68-72°F)
Detailed comfort ranges:
- 16-18°C (61-64°F): Cool, good for sleeping
- 18-19°C (64-66°F): Comfortable with warm clothing
- 20-21°C (68-70°F): Ideal for most people during daytime activities
- 22-23°C (72-73°F): Warm and comfortable
- 24-25°C (75-77°F): Getting warm, may need cooling
- Above 26°C (79°F): Uncomfortably warm indoors
Factors affecting comfort:
- Humidity: Higher humidity feels warmer
- Air movement: Fans increase comfort
- Activity level: Exercise generates heat
- Clothing: More clothing allows lower temperatures
- Personal preference: Varies by individual
- Acclimatization: People adapt to local climates
Typical thermostat settings:
- Winter heating: 20°C (68°F)
- Summer cooling: 24°C (75°F)
- Energy savings: Lower in winter (18°C), higher in summer (26°C)
- Office standard: 21-22°C (70-72°F)
At what Celsius temperature does water boil at high altitude?
Water boils at lower temperatures at high altitude because atmospheric pressure decreases:
Boiling point by altitude:
- Sea level (0m): 100°C (212°F)
- 500m (1,640ft): ~98.5°C (209°F)
- 1,000m (3,281ft): ~97°C (207°F)
- 1,500m (4,921ft): ~95°C (203°F)
- 2,000m (6,562ft): ~93°C (199°F)
- 3,000m (9,843ft): ~90°C (194°F)
- 4,000m (13,123ft): ~87°C (189°F)
- 5,000m (16,404ft): ~83°C (181°F)
- 8,849m (29,032ft - Mt. Everest): ~71°C (160°F)
Rule of thumb: Water's boiling point decreases by approximately 1°C for every 300m (or 1°F per 500ft) increase in elevation.
Why this matters:
- Cooking times increase: Food takes longer to cook at lower boiling temperatures
- Pasta, rice, vegetables: May need extra time
- Baking adjustments: Recipes may need modification at high altitude
- Tea/coffee brewing: Lower temperature may affect flavor extraction
Is 20°C hot or cold?
20°C (68°F) is generally considered mild to comfortable—neither hot nor cold.
Context matters:
Indoor temperature:
- Perfect room temperature for most people
- Standard thermostat setting in many countries
- Comfortable for light clothing
Outdoor weather:
- Pleasant spring/fall day
- Light jacket or sweater may be comfortable
- Good weather for outdoor activities
Water temperature:
- Cool for swimming
- Tolerable for active swimming, cold for leisure
- Ocean/lake water at 20°C feels refreshing but cool
Sleeping:
- Slightly warm for optimal sleep
- Most people prefer 16-18°C (61-64°F) for sleeping
Cultural/regional perspectives:
- Tropical residents: May find 20°C cold
- Arctic residents: May find 20°C warm
- Temperate zone residents: Find it comfortable and pleasant
Humidity factor:
- 20°C with high humidity feels warmer
- 20°C with low humidity feels cooler
What temperature is dangerous for humans in Celsius?
Dangerously Cold (Hypothermia) - Body Temperature:
- Below 35°C (95°F): Hypothermia begins, shivering
- 32-35°C (89-95°F): Mild hypothermia, confusion, drowsiness
- 28-32°C (82-89°F): Moderate hypothermia, irregular heartbeat
- Below 28°C (82°F): Severe hypothermia, unconsciousness, life-threatening
- Below 24°C (75°F): Usually fatal
Dangerously Hot (Hyperthermia) - Body Temperature:
- 38°C (100.4°F): Fever/heat stress
- 39°C (102.2°F): Moderate fever
- 40°C (104°F): High fever, medical attention needed
- 41°C (105.8°F): Heat stroke risk, emergency
- 42°C (107.6°F): Critical, organ damage begins
- Above 43°C (109.4°F): Usually fatal without rapid cooling
Environmental Temperature Dangers:
Cold:
- Below -40°C (-40°F): Frostbite in minutes, exposed skin freezes
- -30 to -40°C (-22 to -40°F): Extreme cold, survival difficult
- -20 to -30°C (-4 to -22°F): Very cold, proper protection essential
- Below -10°C (14°F): Frostbite risk on exposed skin
Heat:
- Above 35°C (95°F): Heat stress risk, especially with high humidity
- 40-45°C (104-113°F): Heat exhaustion and heat stroke risk
- Above 50°C (122°F): Survival difficult without shade, water, and cooling
- Above 55°C (131°F): Extreme danger, few minutes of exposure can be fatal
Heat Index (temperature + humidity): High humidity makes temperatures feel hotter and increases danger—40°C with high humidity can be more dangerous than 45°C with low humidity.
Why do Americans use Fahrenheit instead of Celsius?
Historical reasons:
1. Early adoption (1720s):
- Fahrenheit scale invented in 1724 by Daniel Gabriel Fahrenheit
- Adopted in English-speaking world, including American colonies
- Celsius wasn't invented until 1742, after Fahrenheit was established
2. Independence (1776):
- US gained independence before metric system was developed (1790s)
- American infrastructure already built around British Imperial system
- No compelling reason to change at the time
3. Metric system resistance:
- France developed metric system in 1790s
- US chose not to adopt metric officially
- Multiple attempts to convert US to metric have failed (notably 1970s)
Cultural and practical reasons:
1. Cultural inertia:
- Generations of Americans learned Fahrenheit
- Emotional attachment to familiar measurements
- "If it ain't broke, don't fix it" mentality
2. Conversion costs:
- Enormous expense to convert infrastructure
- All weather stations, thermostats, ovens, road signs
- Industrial equipment, scientific instruments
- Education system overhaul needed
3. Perceived precision:
- Fahrenheit has smaller degree increments
- 1°F = 0.56°C (finer granularity)
- Some argue this is more precise for everyday use
Current status:
Fahrenheit domains (US):
- Weather forecasts
- Household thermostats
- Cooking temperatures (ovens)
- Public discourse
Celsius domains (US):
- Scientific research (NASA, universities)
- Military
- Medical (increasingly)
- International trade/diplomacy
Other Fahrenheit users: Only 3 countries primarily use Fahrenheit: United States, Bahamas, Cayman Islands. The rest of the world (190+ countries) uses Celsius.
Practical impact:
- Americans traveling abroad must learn Celsius
- International collaboration requires conversion
- Many Americans now learn both scales
- US is increasingly isolated in temperature measurement
Use our Fahrenheit to Celsius converter to easily switch between scales.
What is normal body temperature in Celsius?
Normal body temperature: 36.5-37.5°C (97.7-99.5°F)
Average: 37°C (98.6°F)
Important factors affecting body temperature:
1. Time of day:
- Morning (6 AM): Lower, around 36.3°C (97.3°F)
- Afternoon/Evening (6 PM): Higher, around 37.3°C (99.1°F)
- Daily variation: About 0.5-1°C difference
2. Measurement location:
- Rectal: 0.5°C (0.9°F) higher than oral (most accurate)
- Oral: Standard reference point
- Ear (tympanic): Similar to rectal if done correctly
- Armpit (axillary): 0.5°C (0.9°F) lower than oral (least accurate)
- Forehead (temporal): Convenient but less accurate
3. Age:
- Infants: Slightly higher (36.6-37.8°C / 97.9-100°F)
- Children: Similar to adults
- Elderly: May be slightly lower (35.8-36.9°C / 96.4-98.4°F)
4. Activity level:
- Rest: Lower baseline temperature
- Exercise: Can temporarily raise to 38-39°C (100-102°F)
- Digestion: Slightly raises temperature
5. Other factors:
- Menstrual cycle (women)
- Time since eating
- Ambient temperature
- Hydration status
- Circadian rhythm
Body temperature guide:
Below normal:
- Below 35°C (95°F): Hypothermia, medical concern
- 35-36°C (95-96.8°F): Mild hypothermia possible
- 36-36.5°C (96.8-97.7°F): Lower end of normal
Normal range:
- 36.5-37.5°C (97.7-99.5°F): Normal healthy range
- 37°C (98.6°F): Classic "normal" temperature (average)
Elevated/Fever:
- 37.5-38°C (99.5-100.4°F): Slightly elevated, monitor
- 38-39°C (100.4-102.2°F): Low-grade fever
- 39-40°C (102.2-104°F): Moderate fever, monitor closely
- Above 40°C (104°F): High fever, seek medical attention
Measurement best practices:
- Wait 30 minutes after eating/drinking/exercise before measuring
- Use same method consistently for comparison
- Digital thermometers most accurate for home use
- For infants: rectal measurement most reliable
How many degrees Celsius is freezing?
Water freezes at 0°C (32°F) at standard atmospheric pressure (sea level, 1 atmosphere).
What "freezing" means:
- 0°C: Temperature at which water transitions from liquid to solid (ice)
- Below 0°C: Water is solid (ice, snow)
- Above 0°C: Ice melts to liquid water
- Exactly 0°C: Water and ice can coexist in equilibrium
This is a defining point: The Celsius scale is specifically defined with 0°C as the freezing point of pure water, making it an intuitive and memorable reference.
Factors affecting freezing point:
1. Salinity:
- Pure water: 0°C (32°F)
- Seawater (~3.5% salt): ~-2°C (28°F)
- Saturated salt solution: ~-21°C (-6°F)
2. Pressure:
- Higher pressure: Slightly lowers freezing point
- Lower pressure: Slightly raises freezing point
- Effect is small: About -0.0075°C per atmosphere
3. Impurities/additives:
- Sugar: Lowers freezing point (ice cream stays soft)
- Alcohol: Significantly lowers freezing point (vodka freezes at -27°C)
- Antifreeze (ethylene glycol): Lowers to -37°C (50/50 mix)
- Road salt (calcium chloride): Melts ice down to -25°C
Weather context:
Freezing conditions:
- Below 0°C: Freezing, snow and ice form, water pipes at risk
- 0 to -5°C: Light freeze, frost forms overnight
- -5 to -10°C: Moderate freeze, icy roads
- Below -10°C: Hard freeze, outdoor activities limited
Near-freezing:
- 0-2°C: Just above freezing, frost possible
- 2-5°C: Cool, generally no freezing concerns
- 5-10°C: Cold but no freeze risk
Freezer temperatures:
- -18°C (0°F): Standard home freezer (well below freezing)
- -20°C (-4°F): Deep freeze
- -40°C (-40°F): Ultra-cold freeze (commercial/research)
Why 0°C matters:
- Frost warnings issued when temperature drops below 0°C
- Roads ice over below 0°C
- Outdoor water pipes freeze below 0°C
- Plants vulnerable to frost damage below 0°C
About Fahrenheit (°F)
Why does the US use Fahrenheit?
The United States uses Fahrenheit due to historical adoption, infrastructure investment, and cultural resistance to change.
Historical reasons:
- Fahrenheit scale adopted in 1700s when US was British colony
- Became deeply embedded in American culture
- All infrastructure built around Fahrenheit (thermostats, ovens, etc.)
Why didn't US switch to Celsius?
- Cost: Replacing millions of thermostats, ovens, signs would cost billions
- Cultural resistance: Americans prefer familiar system
- Perceived complexity: Relearning temperature reference points
- Failed metric conversion: 1970s Metric Conversion Act was voluntary and largely unsuccessful
Advantages of Fahrenheit (often cited):
- Finer resolution (1°F = 0.56°C) for everyday temps
- Human comfort range fits roughly 0-100°F
- Weather forecasts use whole numbers more often
Current status:
- US is only major country using Fahrenheit daily
- Science and medicine use Celsius/Kelvin
- Unlikely to change in near future
How do you convert Fahrenheit to Celsius?
Use the formula: °C = (°F - 32) × 5/9
Step-by-step:
- Subtract 32 from the Fahrenheit temperature
- Multiply the result by 5
- Divide by 9 (or multiply by 5/9)
Examples:
- 68°F: (68 - 32) × 5/9 = 36 × 5/9 = 20°C
- 86°F: (86 - 32) × 5/9 = 54 × 5/9 = 30°C
- 32°F: (32 - 32) × 5/9 = 0°C (freezing point)
- 212°F: (212 - 32) × 5/9 = 100°C (boiling point)
- -40°F: (-40 - 32) × 5/9 = -40°C (same in both!)
Quick approximations:
- Rough estimate: Subtract 30, then divide by 2
- Example: 80°F ≈ (80-30)/2 = 25°C (actual: 26.7°C)
Use our Fahrenheit to Celsius converter for accurate conversions.
What is normal body temperature in Fahrenheit?
Normal human body temperature is 98.6°F (37°C), though the normal range is 97-99°F.
Details:
- Average: 98.6°F (37°C) when measured orally
- Normal range: 97-99°F (individuals vary)
- Varies by: Time of day, activity, measurement method
- Morning: Typically lower (97.0-97.5°F)
- Afternoon: Typically higher (98.5-99.5°F)
Fever thresholds:
- 99-100.4°F: Low-grade fever
- 100.4°F and above: Fever
- 103°F and above: High fever (call doctor)
- Above 105°F: Medical emergency
Measurement variations:
- Oral: 98.6°F (standard)
- Rectal: 99.6°F (1°F higher, most accurate)
- Armpit: 97.6°F (1°F lower, least accurate)
- Ear: ~98.6°F (when done correctly)
At what temperature does water freeze in Fahrenheit?
Water freezes at 32°F (0°C) at standard atmospheric pressure (sea level).
Freezing point details:
- Pure water: Exactly 32°F at sea level
- Salt water: Lower than 32°F (28°F for ocean water)
- Higher elevation: Slightly lower than 32°F
- Lower elevation: Slightly higher than 32°F
Related temperatures:
- Frost formation: 32°F or below
- Black ice: Forms around 32°F
- Sleet: 32-34°F (rain freezing on contact)
- Snow: Requires below 32°F air temperature
Why 32°F?
- Fahrenheit's original scale placed water freezing at 32° based on his reference points
- Not as intuitive as 0°C, but historically established
At what temperature does water boil in Fahrenheit?
Water boils at 212°F (100°C) at standard atmospheric pressure (sea level).
Boiling point details:
- Sea level: 212°F exactly
- Higher elevation: Lower than 212°F (198°F in Denver, CO)
- Lower elevation: Higher than 212°F
- Pressure cooker: Above 212°F (250°F at high pressure)
Elevation effects:
- For every 500 feet above sea level, boiling point drops ~1°F
- Denver (5,280 ft): Water boils at ~202°F
- Mount Everest (29,000 ft): Water boils at ~160°F
Cooking implications:
- High altitude: Longer cooking times needed
- Pressure cookers: Faster cooking due to higher temp
Why 212°F?
- Another fixed point on Fahrenheit's original scale
- 180 degrees between freezing (32°F) and boiling (212°F)
What temperature is considered a fever?
A temperature of 100.4°F (38°C) or higher is generally considered a fever in adults.
Fever categories:
- Normal: 97-99°F
- Low-grade fever: 99-100.4°F
- Mild fever: 100.4-102°F
- Moderate fever: 102-103°F
- High fever: 103-104°F
- Very high fever: Above 104°F (seek medical care)
In children/infants:
- Newborn (0-3 months): 100.4°F or higher (call doctor immediately)
- Infant (3-36 months): 102°F or higher (call doctor)
- Child: 103°F or higher (call doctor)
When to seek medical attention:
- Adult fever above 103°F
- Fever lasting more than 3 days
- Infant under 3 months with any fever
- Fever with severe symptoms (confusion, difficulty breathing)
Measurement note: Rectal temperatures are ~1°F higher, armpit ~1°F lower than oral.
Is -40°F the same as -40°C?
Yes! -40°F = -40°C exactly. This is the only temperature where both scales intersect.
Why this happens:
- The conversion formula: °C = (°F - 32) × 5/9
- At -40: (-40 - 32) × 5/9 = -72 × 5/9 = -40°C
- Mathematically, this is the unique intersection point
Other relationships:
- Below -40: Fahrenheit numbers are smaller than Celsius (e.g., -50°F = -45.6°C)
- Above -40: Fahrenheit numbers are larger (e.g., 0°F = -17.8°C)
Practical context:
- 40° is extremely cold (Arctic/Antarctic conditions)
- Dangerous to humans without proper protection
- Few places on Earth regularly reach this temperature
Fun fact: This is the most commonly cited "trivia" about temperature scales!
What is a comfortable room temperature in Fahrenheit?
68-72°F (20-22°C) is generally considered comfortable room temperature for most people.
Comfort ranges by activity:
- Sleeping: 60-67°F (cooler is better)
- Living areas: 68-72°F
- Working: 68-76°F
- Exercising indoors: 65-68°F
Factors affecting comfort:
- Humidity: Lower humidity feels warmer
- Air movement: Fans make it feel cooler
- Clothing: Dress code affects ideal temp
- Personal preference: Varies significantly
- Age: Elderly prefer warmer (72-78°F)
Energy recommendations:
- Department of Energy: 78°F summer, 68°F winter
- OSHA workplace: 68-76°F
- Energy saving: Adjust 7-10°F when away or sleeping
International differences:
- US comfort: 68-72°F average
- Europe comfort: 68-73°F (20-23°C)
- Tropical regions: 75-80°F normal
How do you convert Celsius to Fahrenheit?
Use the formula: °F = (°C × 9/5) + 32
Step-by-step:
- Multiply the Celsius temperature by 9
- Divide by 5 (or multiply by 9/5 = 1.8)
- Add 32
Examples:
- 20°C: (20 × 9/5) + 32 = 36 + 32 = 68°F
- 30°C: (30 × 9/5) + 32 = 54 + 32 = 86°F
- 0°C: (0 × 9/5) + 32 = 32°F (freezing point)
- 100°C: (100 × 9/5) + 32 = 212°F (boiling point)
- -40°C: (-40 × 9/5) + 32 = -40°F (same in both!)
Quick approximations:
- Double the Celsius temp and add 30
- Example: 20°C ≈ (20×2)+30 = 70°F (actual: 68°F)
Use our Celsius to Fahrenheit converter for accurate conversions.
What countries use Fahrenheit?
Very few countries use Fahrenheit today. The United States is the primary user.
Current Fahrenheit users:
- United States (primary user for daily temperatures)
- Bahamas (some usage)
- Belize (some usage)
- Cayman Islands
- Palau
- Federated States of Micronesia
- Marshall Islands
US territories using Fahrenheit:
- Puerto Rico
- US Virgin Islands
- Guam
- American Samoa
Former users (switched to Celsius):
- United Kingdom: Switched 1960s-1970s
- Canada: Switched 1970s
- Australia: Switched 1970s
- New Zealand: Switched 1970s
- South Africa: Switched 1960s-1970s
Rest of world: Uses Celsius exclusively (195+ countries)
In science/medicine: Even US uses Celsius and Kelvin for scientific work.
What is the difference between Fahrenheit and Celsius?
Fahrenheit and Celsius are different temperature scales with different zero points and degree sizes.
Key differences:
| Feature | Fahrenheit | Celsius | |---------|-----------|---------| | Freezing point of water | 32°F | 0°C | | Boiling point of water | 212°F | 100°C | | Degrees between | 180° | 100° | | Absolute zero | -459.67°F | -273.15°C | | Degree size | Smaller (1°F = 0.56°C) | Larger (1°C = 1.8°F) | | Primary users | USA, few others | Rest of world (195+ countries) |
Conversion:
- °C = (°F - 32) × 5/9
- °F = (°C × 9/5) + 32
Intersection point: -40°F = -40°C (only place scales match)
Practical differences:
- Celsius is simpler (0° freeze, 100° boil)
- Fahrenheit provides finer resolution
- Celsius aligned with metric system
- Fahrenheit embedded in US culture
People Also Ask
How do I convert Celsius to Fahrenheit?
To convert Celsius to Fahrenheit, enter the value in Celsius in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our temperature converter page to convert between other units in this category.
Learn more →What is the conversion factor from Celsius to Fahrenheit?
The conversion factor depends on the specific relationship between Celsius and Fahrenheit. 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 Fahrenheit back to Celsius?
Yes! You can easily convert Fahrenheit back to Celsius by using the swap button (⇌) in the calculator above, or by visiting our Fahrenheit to Celsius converter page. You can also explore other temperature conversions on our category page.
Learn more →What are common uses for Celsius and Fahrenheit?
Celsius and Fahrenheit are both standard units used in temperature measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our temperature converter for more conversion options.
For more temperature conversion questions, visit our FAQ page or explore our conversion guides.
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All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — International Temperature Scale standards
Bureau International des Poids et Mesures — Definition of the kelvin and temperature scales
Last verified: February 19, 2026