Converter

Temperature Converter

Convert between Fahrenheit, Celsius, and Kelvin with conversion formulas shown. Includes a visual thermometer and notable temperature reference points.

Quick Answer

°F to °C: subtract 32, multiply by 5/9. °C to °F: multiply by 9/5, add 32. °C to K: add 273.15. Water freezes at 32°F / 0°C and boils at 212°F / 100°C.

Convert Temperature

Enter a temperature and select units to convert.

100 °F
37.78 °C
°C = (°F − 32) × 5/9
37.78°C
Fahrenheit
100 °F
Celsius
37.78 °C
Kelvin
310.93 K

Conversion Formulas

°F = (°C × 9/5) + 32

°C = (°F − 32) × 5/9

K = °C + 273.15

Notable Temperatures

Reference°F°CK
Absolute Zero
Lowest possible temperature		-459.67-273.150
Water Freezes
Freezing point of water at 1 atm		320273.15
Room Temperature
Typical indoor temperature		71.622295.15
Body Temperature
Normal human body temp		98.637310.15
Water Boils
Boiling point of water at 1 atm		212100373.15

About This Tool

The Temperature Converter provides instant, accurate conversions between the three most commonly used temperature scales: Fahrenheit, Celsius, and Kelvin. Unlike length or weight conversions which use simple multiplication factors, temperature conversions involve both multiplication and addition, making a converter tool particularly useful.

Understanding Temperature Scales

The Celsius scale (also called centigrade) sets water's freezing point at 0° and boiling point at 100° at standard atmospheric pressure, making it intuitive for everyday use. Fahrenheit sets these at 32° and 212° respectively, with the human body temperature originally intended to be 100°F (it is actually about 98.6°F). Kelvin uses the same increment size as Celsius but starts at absolute zero, making it the standard for scientific work.

When Each Scale Is Used

Celsius is used by most countries worldwide for weather, cooking, and everyday temperature references. Fahrenheit is primarily used in the United States, its territories, and a few Caribbean nations. Kelvin is the SI unit used universally in science, engineering, and when absolute temperature measurements are needed. Color temperature in photography and lighting is also expressed in Kelvin.

Quick Mental Conversion Tips

For a rough Fahrenheit to Celsius conversion, subtract 30 and divide by 2. For Celsius to Fahrenheit, double and add 30. These shortcuts give results within a few degrees of the actual value, which is close enough for deciding what to wear or setting a thermostat. For precise calculations, always use the exact formulas shown above.

Frequently Asked Questions

How do I convert Fahrenheit to Celsius?
Subtract 32 from the Fahrenheit temperature, then multiply by 5/9. The formula is: °C = (°F − 32) × 5/9. For example, 72°F = (72 − 32) × 5/9 = 22.2°C. For a quick mental estimate, subtract 30 and divide by 2 (gives 21°C for 72°F, close enough for everyday use).
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8), then add 32. The formula is: °F = (°C × 9/5) + 32. For example, 37°C = (37 × 1.8) + 32 = 98.6°F. For a quick mental estimate, double the Celsius value and add 30 (gives 104°F for 37°C, slightly off but useful for rough estimates).
What is Kelvin and when is it used?
Kelvin is the SI base unit of temperature used primarily in science and engineering. It starts at absolute zero (0 K = −273.15°C), the theoretical lowest temperature where all molecular motion ceases. To convert Celsius to Kelvin, simply add 273.15. Kelvin uses the same degree increments as Celsius (a 1°C change equals a 1 K change), making it easy to work with. It is used in physics, chemistry, astronomy, and color temperature specifications.
What is absolute zero?
Absolute zero is 0 Kelvin, −273.15°C, or −459.67°F. It is the theoretical lowest temperature possible, where particles have minimal vibrational motion. While absolute zero cannot be perfectly achieved in practice, scientists have cooled materials to within billionths of a degree above it. At near-absolute-zero temperatures, exotic quantum phenomena like superconductivity and Bose-Einstein condensation occur.
At what temperature are Fahrenheit and Celsius equal?
− 40 degrees is the point where Fahrenheit and Celsius scales intersect. At −40°F = −40°C. This can be verified with the conversion formula: (−40 − 32) × 5/9 = −72 × 5/9 = −40. This curious intersection is sometimes used as a fun trivia question or teaching example in math and science classes.

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