Temperature unit converter

Temperature is not converted by multiplying a factor: each scale has its own zero point, so an affine transformation is required.

This converter covers the four scales used in science and daily life.

Everything is converted to kelvin first, the absolute scale, and from there to the target unit. If a result would fall below absolute zero, the tool detects it and warns you.

The kelvin takes no degree sign because it is not a relative scale

Celsius and Fahrenheit place their zero at an arbitrary point, so their values are degrees above or below that reference. The kelvin starts at absolute zero, the lowest possible temperature, which makes it an absolute scale: you write 300 K, not 300 °K. The correction was adopted officially in 1967.

Absolute zero is unreachable

At minus 273.15 degrees Celsius thermal motion ceases. Thermodynamics proves it is impossible to reach exactly, although physics laboratories have come within billionths of a degree. It is a theoretical limit, not a technical obstacle.

The Rankine scale

It is to Fahrenheit what the kelvin is to Celsius: an absolute scale with Fahrenheit-sized degrees. It is used in some branches of engineering in the United States, particularly applied thermodynamics.

Converting differences

An increase of one kelvin is exactly an increase of one degree Celsius, because both scales share the same degree size and differ only in origin. When working with changes rather than absolute temperatures, the two scales are interchangeable.