Fahrenheit to Kelvin
Convert Fahrenheit to kelvin — type a temperature in either box. The formula is K = (°F − 32) × 5/9 + 273.15.
How to use
- Enter a temperature in the Fahrenheit field.
- The Kelvin value updates instantly.
- Negative values work exactly the same way.
- Check the reference table for the fixed points.
Fahrenheit to Kelvin formula
Temperature is the one conversion that needs more than a multiplication: the scales disagree about where zero sits, so an offset is required as well as a ratio.
K = (°F − 32) × 5/9 + 273.15
The order of operations matters: follow the formula exactly as written above.
Worked example
Converting 100 °F gives 310.93 K.
100 °F → 310.93 K
Reference points
Four temperatures worth memorizing, in both scales:
| Reference point | Fahrenheit | Kelvin |
|---|---|---|
| water freezing | 32 °F | 273.15 K |
| a mild room | 68 °F | 293.15 K |
| body temperature | 98.6 °F | 310.15 K |
| water boiling | 212 °F | 373.15 K |
What is a degree Fahrenheit?
Fahrenheit is the everyday temperature scale in the United States, with water freezing at 32 °F and boiling at 212 °F.
Definition: Defined against Celsius: °F = °C × 9/5 + 32. The 180-degree span between freezing and boiling gives it finer granularity than Celsius.
Where it is used: US weather, cooking, oven settings and body temperature.
Worth knowing: The two scales cross at −40°, where −40 °C and −40 °F are the same temperature.
What is a kelvin?
The kelvin is the SI base unit of thermodynamic temperature, counting from absolute zero rather than from a property of water.
Definition: Since 2019 defined by fixing the Boltzmann constant at exactly 1.380649×10⁻²³ joules per kelvin. Absolute zero is 0 K, which is −273.15 °C.
Where it is used: Physics and chemistry, color temperature of lighting, and astronomy.
Worth knowing: Written 'kelvin', not 'degrees kelvin', and the symbol K takes no degree sign.
Frequently asked questions
What is the formula to convert Fahrenheit to kelvin?
Use K = (°F − 32) × 5/9 + 273.15.
What is 0 °F in kelvin?
0 °F is 255.37 K.
What is 100 °F in kelvin?
100 °F is 310.93 K.
Does this work for negative temperatures?
Yes. The formula is linear, so it is valid above and below zero on either scale.
Is there anything to watch out for with fahrenheit?
The two scales cross at −40°, where −40 °C and −40 °F are the same temperature.
Is there anything to watch out for with kelvin?
Written 'kelvin', not 'degrees kelvin', and the symbol K takes no degree sign.