Fahrenheit to Kelvin Converter (°F to K)

Engineering and science data from the United States often arrive in Fahrenheit, while the equations that use them, for gas behavior, heat radiation or thermal efficiency, need an absolute scale. Kelvins are the SI choice. The conversion moves the zero to absolute zero by adding 459.67 and then shrinks the number by 5/9, since a kelvin is 1.8 times as large as a Fahrenheit degree.

Some US engineering texts use the Rankine scale instead, which starts at absolute zero but keeps Fahrenheit-sized degrees, so °R = °F + 459.67 and K = °R × 5/9. The first chart lists cryogenic and everyday values; the second runs from 0 K upward and includes about 255.37 K, the kelvin value of 0 °F.

How to use this tool

1. Type a value in the Fahrenheit box to see it in kelvins, or type in the Kelvin box to convert the other way.
2. Press ⇄ to swap the two units, or Load example for a typical value.
3. Check the charts below for common values; for other units, open the Temperature converter.

Formula

K = (°F + 459.67) × 5/9

°F = K × 9/5 − 459.67

The scales have different zero points, so the formula adds or subtracts an offset as well as multiplying.

Example

Two conversions worked with the same factors the converter uses:

70 °F ≈ 294.261 K

300 K = 80.33 °F

Fahrenheit to Kelvin chart

Common values from degrees Fahrenheit to kelvins, rounded to four decimal places.

Kelvin to Fahrenheit chart

The reverse direction for values people often look up.

Cold and hot points often quoted in Fahrenheit

Quick mental estimate

Subtract 32, take about 5/9 by halving and adding a tenth of the half, then add 273: 70 °F → 38 → 19 + 1.9 = 20.9 → 293.9 K, against an exact 294.26 K. The 5/9 step comes out 1% small, so the estimate is about 1 K off at the boiling point of water and much closer near room temperature.

Use the converter or the charts when the exact figure matters.

The two units

Fahrenheit (°F): Fahrenheit temperature is defined by °F = °C × 9/5 + 32. Thus 0 °C equals exactly 32 °F, 100 °C equals exactly 212 °F, and absolute zero is −459.67 °F.

Kelvin (K): The kelvin is the SI base unit of thermodynamic temperature, defined since 2019 by fixing the Boltzmann constant at exactly 1.380649 × 10⁻²³ J/K. The scale starts at absolute zero (0 K), and 0 °C is exactly 273.15 K.