How to Use This Tool

Temperature converter

Type a temperature into any field and the converter fills in the rest. It handles Fahrenheit, Celsius, and Kelvin. Unlike weight or length conversions, temperature conversion is not a simple multiplication. Each scale has a different zero point, so the formulas involve both multiplication and addition.

Common temperature conversions

Temperature conversion formulas

Fahrenheit to Celsius

°C = (°F – 32) x 5/9

Example: 98.6°F. Subtract 32 to get 66.6. Multiply by 5/9 to get 37°C. That is normal human body temperature.

Celsius to Fahrenheit

°F = (°C x 9/5) + 32

Example: 25°C. Multiply by 9/5 to get 45. Add 32 to get 77°F. A warm spring day.

Celsius to Kelvin

K = °C + 273.15

Example: 100°C + 273.15 = 373.15 K. The boiling point of water at sea level.

Kelvin to Celsius

°C = K – 273.15

Example: 0 K – 273.15 = -273.15°C. That is absolute zero, the coldest possible temperature.

Fahrenheit to Kelvin

K = (°F – 32) x 5/9 + 273.15

Example: 72°F. Subtract 32 to get 40. Multiply by 5/9 to get 22.22. Add 273.15 to get 295.37 K.

When you need temperature conversions

Cooking and baking

American recipes set oven temperatures in Fahrenheit. European and Australian recipes use Celsius. A recipe that says 350°F means 177°C. Most ovens outside the US have Celsius dials, and getting the conversion wrong by even 20°C can burn or undercook food.

Weather and travel

Weather forecasts in the US use Fahrenheit. Almost everywhere else uses Celsius. When a forecast in Paris says 30°C, that is 86°F. Knowing that 0°C is freezing and 30°C is hot covers most weather situations without doing exact math.

Health and medicine

US thermometers read Fahrenheit. A normal temperature is 98.6°F (37°C). A fever starts around 100.4°F (38°C). Many digital thermometers can switch between scales, but knowing the conversion helps when reading medical advice from other countries.

Science and engineering

Scientific work uses Celsius or Kelvin. Kelvin is the SI unit and starts at absolute zero, which makes it useful in physics, chemistry, and engineering where negative temperatures would complicate calculations. The size of a degree is the same in Celsius and Kelvin, so converting between them is just adding or subtracting 273.15.

Quick mental math

For Fahrenheit to Celsius, subtract 30, then divide by 2. This gives a rough estimate. At 80°F: 80 – 30 = 50, divided by 2 = 25°C. The precise answer is 26.7°C, so the shortcut is off by less than 2 degrees. Good enough to decide what to wear.

For Celsius to Fahrenheit, double the Celsius number and add 30. At 20°C: 20 x 2 = 40, plus 30 = 70°F. The precise answer is 68°F. Again, close enough for everyday use.

Some round numbers are worth memorizing: 0°C = 32°F (freezing), 10°C = 50°F (chilly), 20°C = 68°F (comfortable), 30°C = 86°F (hot), 37°C = 98.6°F (body), 100°C = 212°F (boiling).

Tips for accurate conversions

• The formulas for Fahrenheit and Celsius are not symmetric. To go from F to C you subtract 32 first, then multiply. To go from C to F you multiply first, then add 32. Mixing up the order gives a wrong answer.
• Kelvin never uses a degree symbol. It is written as 300 K, not 300°K. This is a common formatting error.
• Water boils at 100°C only at sea level. At higher altitudes, the boiling point drops. In Denver (5,280 feet), water boils at about 95°C (203°F). This affects cooking times for boiled foods.
• Negative 40 is the same in both Fahrenheit and Celsius. Itis the only temperature where the two scales intersect.

The three temperature scales

Daniel Fahrenheit introduced his scale in 1724, setting 0 at the coldest temperature he could create with a salt-ice-water mixture and 96 at human body temperature (later refined to 98.6). Anders Celsius proposed his scale in 1742, originally with 0 as the boiling point and 100 as freezing. It was inverted after his death to the form used today.

Lord Kelvin introduced the absolute temperature scale in 1848. It uses the same degree size as Celsius but starts at absolute zero (-273.15°C), the theoretical point where all molecular motion stops. Kelvin is the SI base unit for temperature and is used in all scientific work where an absolute reference matters.

Frequently asked questions

What is 72°F in Celsius?

72°F = 22.2°C. That is a comfortable indoor temperature.

What is 0°C in Fahrenheit?

0°C = 32°F. Water freezes at this temperature at standard pressure.

What is normal body temperature?

37°C or 98.6°F. This is an average. Normal body temperature varies slightly by person, time of day, and measurement method. Recent studies suggest the average has drifted down to about 36.6°C (97.9°F).

What is absolute zero?

Absolute zero is 0 K, which equals -273.15°C or -459.67°F. It is the lowest possible temperature, where atoms have minimal thermal energy.

What is 350°F in Celsius?

350°F = 176.67°C. Most ovens round this to 180°C.

What is the difference between Celsius and centigrade?

They are the same scale. “Centigrade” was the original name. It was officially renamed to Celsius in 1948 to avoid confusion with the centesimal grade used in some angular measurements.

Why does the US use Fahrenheit?

The US adopted Fahrenheit in the colonial era, when it was the standard in the British Empire. Britain later switched to Celsius, but the US did not follow. The Metric Conversion Act of 1975 made metric use voluntary, and Fahrenheit remained the everyday standard.

Can any temperature be negative in Kelvin?

No. The Kelvin scale starts at absolute zero (0 K). Negative Kelvin values do not exist in classical thermodynamics.

Related conversion tools

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• Feet to Meters Converter
• Miles to Kilometers Converter

Measurement guides

• How Big Is X Inches? A Visual Size Guide From 1 to 16 Inches
• Inches Explained: Conversion Chart, Tools, and Real-World Examples

Formula & Explanation

Temperature conversions are non-linear because the Fahrenheit and Celsius scales have different zero points. Use the formulas above rather than a simple multiplication factor.