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Temperature Conversion Formulas

The exact formulas for converting between Fahrenheit, Celsius and Kelvin — the standard scales used in the US (Fahrenheit), the rest of the world (Celsius) and science (Kelvin).

Fahrenheit to Celsius

degrees

°C = (°F − 32) × 5/9

Example: 98.6 °F → (98.6 − 32) × 5/9 = 37.0 °C

Celsius to Fahrenheit

degrees

°F = (°C × 9/5) + 32

Example: 20 °C → (20 × 9/5) + 32 = 68 °F

Celsius to Kelvin

kelvin

K = °C + 273.15

Example: 0 °C → 273.15 K

Kelvin to Celsius

degrees

°C = K − 273.15

Example: 300 K → 26.85 °C

Water reference points

degrees

0 °C = 32 °F = 273.15 K

Example: Freezing point of water at 1 atm (standard textbook values)

Body temperature

degrees

98.6 °F = 37.0 °C

Example: Common average human body temperature (standard medical reference)

Practice the conversion too

These examples convert US customary to metric using the exact NIST / SI constants. Open a converter to check any value:

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Frequently Asked Questions

Why does the US use Fahrenheit?

The US customary system uses Fahrenheit for everyday temperature. It was the standard scale when the US formed, and remains in daily use for weather and cooking.

What is the formula from °F to °C in words?

Subtract 32, then multiply by 5/9. The 32 removes the freezing-point offset; the 5/9 scales the remaining size of a degree.

Is 0 °C the same as 0 °F?

No. 0 °C = 32 °F (freezing point of water). 0 °F is much colder (−17.8 °C). They only coincide at −40°, where −40 °F = −40 °C.

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Last Updated 2026 | Formulas are standard textbook content; conversion constants trace to NIST SP 330 & the BIPM SI Brochure.