Temperature Converter (Celsius, Fahrenheit, Kelvin)

Converts a temperature between Celsius, Fahrenheit and kelvin. Give the unit as C, F or K, so Fahrenheit converts to Celsius just as easily as the other way round.

Explanation

Enter a temperature and choose its unit (C, F or K), and all three scales follow. Celsius converts to Fahrenheit exactly as easily as Fahrenheit converts back.

The formulas

°F = °C \times \dfrac{9}{5} + 32 \qquad °C = (°F - 32) \times \dfrac{5}{9}

K = °C + 273.15

Temperature is the one conversion that needs more than a multiplication. The scales put their zeros in different places, so there is a 32 to add or subtract.

Example

Convert 25 °C.

25 \times \dfrac{9}{5} + 32 = 45 + 32 = 77\ °F

In kelvin it is $25 + 273.15 = 298.15$ K.

Reference points

0 °C = 32 °F, water freezes
20 °C = 68 °F, a comfortable room
37 °C = 98.6 °F, body temperature
100 °C = 212 °F, water boils

−40 reads the same on both scales. It is the single temperature where the two rulers cross.

Absolute zero

The kelvin scale starts at absolute zero: nothing can be colder than 0 K, which is −273.15 °C. Molecular motion has stopped and there is nothing left to take away.

Its degrees are the same size as Celsius degrees, so a temperature *difference* is the same number whether you call it °C or K.