Convert temperature instantly between Fahrenheit (°F), Celcius (°C) and Kelvin (K). Change any number in the form or use the slider.

## Temperature Calculations

Three temperature scales are commonly used. These are Celcius, Fahrenheit and Kelvin.

The Fahrenheit temperature scale was originally used in English-speaking countries. The Celsius temperature scale was used in most other countries and for scientific purposes worldwide.

Since the 1970s, most English-speaking countries have officially adopted the Celsius scale.

The Kelvin temperature scale is the base unit of thermodynamic temperature measurement in the International System (SI) of measurement. The Kelvin is the primary unit of temperature measurement in the physical sciences.

### Celcius

The Celcius scale (or centigrade) was originally based on the linear expansion of a narrow mercury column. It is based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure (sea level).

### Fahrenheit

The Fahrenheit scale was also based on the linear expansion of mercury. Originally it used the freezing temperature of a solution of brine (0 °F) and the freezing point of water (32 °F) as reference points. Nowadays it is defined by two fixed points, which are 180 °F apart. The temperature at which water freezes into ice is defined as 32 °F, and the boiling point of water is defined as 212 °F. These should be measured at sea level at 1 atm pressure.

### Kelvin

The Kelvin is the primary unit used for measuring temperature in the physical sciences. It has the same magnitude as Celcius, but 0 Kelvin (0 K) is defined as the absolute zero temperature, or “infinite cold”. This is equivalent to -273.15 °C. Note that in the Kelvin scale we do not use the degree symbol (°) but just the symbol K.

### Formulas

Conversion of temperatures between the different scales can be done with the following formulas:

or

K = 5/9 ( °F + 459.67 )

or

°F = 9/5 ( K ) – 459.67