Temperature Converter

Convert a temperature into all three scales at once, with the exact formula shown so you can check the arithmetic yourself or do it on paper next time.

How it works

Celsius and Fahrenheit are both relative scales with different zero points and different step sizes: a Fahrenheit degree is five ninths of a Celsius degree, and 0 °C sits at 32 °F. Converting therefore needs both a multiplication and a shift, which is why the two numbers do not simply scale.

Kelvin is an absolute scale. Its step size is the same as Celsius, so only the offset changes: 0 K is absolute zero, −273.15 °C. That is why Kelvin has no degree symbol and never goes negative.

Formula

These are the exact definitions; the calculator converts your input to Celsius first, then out to the other two.

• °F = °C × 9/5 + 32
• °C = (°F − 32) × 5/9
• K = °C + 273.15
• °C = K − 273.15

Worked example

100 °C is 100 × 9/5 + 32 = 212 °F, the boiling point of water at sea level, and 100 + 273.15 = 373.15 K. In the other direction, 98.6 °F is (98.6 − 32) × 5/9 = 37 °C.

Assumptions

Conversions are exact and assume no rounding in the source value. Values below absolute zero are rejected, since no physical temperature is lower. The page does not correct for the small difference between the old and current definitions of the Celsius scale, which is irrelevant outside a metrology lab.

Reading the result

Two reference points make the scales easy to sanity-check: −40 is the same number in Celsius and Fahrenheit, and normal body temperature is about 37 °C or 98.6 °F. Weather forecasts in Fahrenheit feel roughly twice as granular as Celsius because each Fahrenheit degree is smaller, so a change of 5 °F is under 3 °C. For cooking, oven temperatures are usually quoted in both, but fan-assisted ovens run about 20 °C cooler than the dial says.

For general information only. Use calibrated instruments where precision matters.

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