Fahrenheit to Kelvin Converter
Type in either box. Two conversions in one: rescale the degree, then move the zero to absolute zero.
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Two conversions in one
Fahrenheit to kelvin is the longest route on this page, because the two scales share neither their zero nor the size of their degree. It is really two conversions stacked: Fahrenheit to Celsius, then Celsius to kelvin.
K = ( °F − 32 ) ÷ 1.8 + 273.15
Take the 32 off to measure the gap above freezing in Fahrenheit degrees. Divide by 1.8 to re-express that gap in the larger Celsius-sized degrees, which are also kelvin-sized. Then add 273.15 to move the zero down to absolute zero.
Collapsed into a single step it becomes K = °F × 5/9 + 255.372…, which is what the working below uses. The two forms give identical answers; the stacked version is easier to remember, the collapsed version easier to type into a spreadsheet.
The working, step by step
Every line updates with whatever you type above. Temperature is the one conversion where the method genuinely matters, because two things change at once: the size of a degree and the position of zero.
Why it is a line that misses the origin
Plotting one scale against the other shows the whole relationship at a glance. The slope is the size of a degree. The height at which the line crosses the vertical axis is the offset — the reason multiplying alone never works. Converting kilograms to pounds gives a line through (0, 0); this one does not.
The same temperature, two different numbers
One physical temperature, read off two scales. The tick marks are spaced differently and shifted along, which is exactly what the two numbers in the formula are doing.
Where does that sit?
A reading is easier to judge against temperatures you already know.
Your turn
Reading a method and being able to use it are different things. Answer within half a per cent and it counts as correct.
Score: 0 of 0
How to use this converter
- Type into either box. The other side updates as you go. There is no button to press.
- Negative readings are fine. Type a minus sign and the graph and scale below follow the value below zero.
- Swap the direction with the button between the boxes if you want to work the other way round.
- Set the decimals if the default is more or less precision than you need.
- Copy the answer with its unit, ready to paste.
- Share the result. The address bar tracks what you type, so the link you copy opens on the same reading.
If you enter something colder than absolute zero, the tool will say so rather than quietly converting a temperature that cannot exist.
Common uses and tips
Where this comes up
- American engineering with SI formulas. Instrumentation reports in Fahrenheit, thermodynamics demands absolute temperature, and this conversion sits between them.
- Combustion and HVAC calculations, where efficiency figures depend on absolute temperature ratios and a Fahrenheit reading cannot be used directly.
- Materials datasheets, which often quote a service temperature in Fahrenheit while the property tables beneath are in kelvin.
Tips worth knowing
- Do it in two moves if you are working by hand. Getting to Celsius first is easier to check than one long expression, and a wrong intermediate value is obvious.
- Differences drop the offset entirely. A rise of 18 °F is a rise of 10 K.
- The floor is −459.67 °F. That is 0 K. Any Fahrenheit reading below it is impossible.
Readings people look up most
Each one opens the converter with the number already in it.
- -459.67 °F to K
- -320 °F to K
- 0 °F to K
- 32 °F to K
- 50 °F to K
- 68 °F to K
- 77 °F to K
- 98.6 °F to K
- 212 °F to K
- 350 °F to K
Quick reference
| Fahrenheit | Kelvin | Usually this is… |
|---|---|---|
| −459.67 °F | 0 K | absolute zero |
| −320.4 °F | 77 K | liquid nitrogen boils |
| 0 °F | 255.37 K | home freezer |
| 32 °F | 273.15 K | water freezes |
| 68 °F | 293.15 K | room temperature |
| 77 °F | 298.15 K | standard lab conditions |
| 98.6 °F | 310.15 K | body temperature |
| 212 °F | 373.15 K | water boils |
| 350 °F | 449.82 K | moderate oven |
Questions people ask
What is the formula for Fahrenheit to kelvin?
K = (°F − 32) ÷ 1.8 + 273.15, or equivalently K = °F × 5/9 + 255.372.
Why are there two numbers to add?
There are not, once the expression is collapsed. The 32 and the 273.15 combine into a single offset of 255.372 after the division is folded in.
What is 0 °F in kelvin?
255.37 K. Zero Fahrenheit is an ordinary cold night, not anywhere near absolute zero.
What is the lowest possible Fahrenheit reading?
−459.67 °F, which is 0 K. Nothing can be colder.