Kelvin to Fahrenheit Converter

Kelvin is the SI base unit of temperature. It begins at absolute zero, the coldest temperature possible, and its degree size is identical to the Celsius degree, so 0 °C is 273.15 K exactly.

Kelvin is used in science and engineering, especially thermodynamics, astronomy, cryogenics and gas calculations, where temperatures must be measured from absolute zero rather than from a water reference point.

Kelvin shares the Celsius degree size, so a temperature difference of one kelvin equals a difference of one degree Celsius. The scales differ only by the offset of 273.15.

A common error is writing a Celsius value with the kelvin symbol; 25 °C is 298.15 K, and 25 K is far colder. Kelvin is written without a degree symbol, and ordinary temperatures are never negative on this scale.

Kelvin is the outlier in its dimension because its zero is absolute zero, while Celsius and Fahrenheit place their zeros at chosen reference points. Weather, cooking and body temperature use those two, and laboratory work uses Kelvin.

Fahrenheit is an affine temperature scale that fixes the freezing point of water at 32 °F and the boiling point at 212 °F at one atmosphere, matching 0 °C and 100 °C.

Fahrenheit remains the everyday scale for weather reporting, cooking oven settings and body temperature in the United States, while science, medicine and most other countries report temperatures in Celsius.

Because Fahrenheit is an offset scale, subtracting 32 first is required; multiplying by 5/9 alone gives a wrong answer. One Fahrenheit degree is five ninths of a Celsius degree.

A frequent mistake is reading a Fahrenheit figure as Celsius, which makes an 80 °F day look like 80 °C on a Celsius-first site. The two scales agree at exactly −40, the single point where both read the same.

Fahrenheit and Celsius are applied to the same jobs, so an oven setting and a weather reading can be misread when the scale is dropped. Kelvin is the third scale, and it stays in scientific use.