# Temperature unit converter

## How to use the temperature unit converter?

The temperature unit converter transforms temperature units to Celsius, Fahrenheit, Kelvin, Rankine and Réaumur. Set the temperature in one of these units and get the result in all the other units.

## Temperature conversion formula

**Celsius to Kelvin:** Kelvin = celsius – 273.15

**Kelvin to Celsius:** Celsius = Kelvin + 273.15

**Fahrenheit to celsius:** Celsius = (Fahrenheit – 32) x 5/9

**Celsius to Fahrenheit:** Fahrenheit = Celsius x 9/5 +32

**Fahrenheit to rankine:** Rankine = Fahrenheit + 459.67

**Rankine to Fahrenheit:** Fahrenheit = Rankine – 459.67

**Celsius to Réaumur:** Réaumure = Celsius x 4/5

**Réaumur to Celsius:** Celsius = Réaumur x 5/4

## About the different temperature units

### Celsius

The Celsius scale, sometimes known by one of its former names, Centigrade scale, is an SI derived unit and so it is used worldwide. However, in the United States, the Bahamas, Belize, the Cayman Islands and Liberia, Fahrenheit remains the preferred scale for everyday temperature.

### Fahrenheit

The definition of the lowest point, that is to say 0 °F, was established as the freezing temperature of a solution of brine. This solution is made from equal parts of ice, water and a salt (ammonium chloride). Further limits were established like the melting point of ice (32 °F) and the average human body temperature (96 °F, about 2.6 °F less than the modern value due to a later redefinition of the scale).

Today the scale is usually defined by the temperature at which water freezes into ice , in other words 32 °F, and the boiling point of water. This latter is defined to be 212 °F. So this means a 180 °F separation, as defined at sea level and standard atmospheric pressure.

Finally, Fahrenheit is used today as the official temperature scale only in the United States (including its unincorporated territories). But also in its freely associated states in the Western Pacific (Palau, the Federated States of Micronesia and the Marshall Islands), the Cayman Islands, and Liberia. Antigua and Barbuda and other islands which use the same meteorological service, such as Saint Kitts and Nevis, the Bahamas, and Belize use Fahrenheit and Celsius. All other countries in the world officially now use the Celsius scale.

### Kelvin

The Kelvin is defined by fixing the numerical value of the Boltzmann constant k to 1.380 649×10^{−23} J⋅K^{−1}. This unit is equal to kg⋅m²⋅s^{−2}⋅K^{−1}, where the kilogram, meter and second are defined in terms of the Planck constant, the speed of light, and the duration of the caesium-133 ground-state hyperfine transition. Thus, this definition depends only on universal constants, and not on any physical artifacts. One Kelvin is equal to a change in the thermodynamic temperature T that results in a change of thermal energy kT by 1.380 649×10^{−23} J. His null point is equal to the absolute zero. The Kelvin is the primary unit of temperature measurement in the physical sciences. But is often used in conjunction with the degree Celsius, which has the same magnitude.

### Rankine

The Rankine scale is an absolute scale of thermodynamic temperature. The 0 on the Rankine is, like for Kelvin, equal to the absolute zero. But a difference in 1 Rankine degree is defined as equal to one Fahrenheit degree, rather than 1 Celsius for the Kelvin scale. It is thus the equivalent of the Kelvin scale, but for Fahrenheit.

### Réaumur

In this temperature scale, the freezing and boiling points of water are defined as 0 and 80 degrees respectively.