Fahrenheit to Kelvin
Convert Fahrenheit to kelvin in one step. Kelvin has no degree sign and no negative values, because it starts at absolute zero.
K = (°F − 32) ÷ 1.8 + 273.15
The kelvin and the degree Celsius share an interval, and the Celsius scale is offset from thermodynamic temperature by 273.15 K exactly.
Kelvin is the scale physics is written in, and it differs from the everyday ones in a way that is easy to miss: it has no degree sign and it never goes negative, because zero is absolute zero rather than an arbitrary reference. A kelvin is the same size as a degree Celsius, so the conversion from Fahrenheit is the Celsius conversion with 273.15 added at the end.
How it is calculated
K = (°F − 32) ÷ 1.8 + 273.15
The subtraction moves the freezing point of water to zero, the division rescales Fahrenheit degrees into Celsius-sized ones, and the addition shifts the origin down to absolute zero. Doing it in that order keeps the arithmetic away from the cancellation that happens if you route through kelvin twice.
Source: The kelvin and the degree Celsius share an interval, and the Celsius scale is offset from thermodynamic temperature by 273.15 K exactly.
Common values
| degrees Fahrenheit | kelvins |
|---|---|
| -459.67 | 0 |
| -40 | 233.15 |
| 0 | 255.37222 |
| 32 | 273.15 |
| 68 | 293.15 |
| 98.6 | 310.15 |
| 212 | 373.15 |
| 500 | 533.15 |
| 1,000 | 810.92778 |
Questions people ask
- What is absolute zero in Fahrenheit?
- Minus 459.67 degrees. That is 0 K, and nothing goes below it — which is why a kelvin figure never carries a minus sign.
- Why is there no degree sign on kelvin?
- It was dropped in 1967. The unit is the kelvin, not the degree kelvin, and it is written 300 K rather than 300 °K.
- Is a kelvin the same size as a degree Fahrenheit?
- No. A kelvin is the same size as a degree Celsius, which is 1.8 times a Fahrenheit degree. That factor is why the division comes before the offset.
- When would I actually need kelvin?
- Anywhere a temperature is multiplied or divided rather than compared: gas laws, blackbody colour temperature, thermal noise. Ratios only mean something on a scale that starts at zero.
Related tools
Celsius to Kelvin
Convert Celsius to Kelvin in your browser. The two scales share a degree size, so only the zero point moves.
Fahrenheit to Celsius
Convert Fahrenheit to Celsius using the exact relation published by NIST, computed in your browser with no detour through kelvin.
Celsius to Fahrenheit
Convert Celsius to Fahrenheit in your browser. Temperature is an offset scale, not a simple multiple, so 0 °C is 32 °F rather than zero.
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