Temperature converter
Celsius, Fahrenheit and Kelvin, all three at once
Type a temperature and pick two scales. The example turns 25 °C into Fahrenheit.
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The same amount in every unit
The formulas
Temperature scales do not share a zero, so they need a formula, not a single factor. Fahrenheit = Celsius × 9/5 + 32. Celsius = (Fahrenheit − 32) × 5/9. Kelvin = Celsius + 273.15. These are the definitions used by the International Bureau of Weights and Measures (SI Brochure) and NIST. The working line under the answer shows the formula with your number in it.
Points to remember
- Water freezes at 0 °C, 32 °F, 273.15 K.
- Water boils at sea level at 100 °C, 212 °F.
- Normal body temperature is about 37 °C, 98.6 °F.
- −40 is the same on both the Celsius and Fahrenheit scales.
Negative temperatures
On a phone, use the Make negative / positive button if your keyboard has no minus key. Absolute zero, −273.15 °C (−459.67 °F, 0 K), is the coldest possible temperature, so anything below it is refused with a message. Kelvin is written without the word degree: 300 K, not 300 °K.
Changes and differences
A change of 1 °C is a change of 1.8 °F (9/5), with no 32 added. This page converts temperatures, not differences. For a Celsius and Fahrenheit chart covering weather, fever and oven settings, see Celsius to Fahrenheit.
Rounding
The answer is worked out from the exact definition, then shown to 4 decimal places (6 significant figures for numbers below 1). It says "exactly" only when nothing was rounded.