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Convert Fahrenheit to Kelvin instantly with the exact formula: K = (°F - 32) × 5/9 + 273.15.
This tool converts a Fahrenheit reading into Kelvin (K), the absolute temperature scale used throughout physics, chemistry, and engineering. Kelvin has no negative values -- its zero point (0 K, "absolute zero") is the coldest physically possible temperature, which is why scientific formulas involving temperature almost always require Kelvin rather than Fahrenheit or Celsius.
Enter a Fahrenheit temperature. The result updates instantly, showing the equivalent in Kelvin and Celsius at the same time.
K = (°F − 32) × 5/9 + 273.15
This is a two-step conversion: first convert Fahrenheit to Celsius (subtract 32, multiply by 5/9), then shift onto the Kelvin scale by adding 273.15 -- the exact offset between Celsius's zero point (water's freezing point) and absolute zero.
| Fahrenheit | Kelvin |
|---|---|
| -459.67°F (absolute zero) | 0.00 K |
| 32°F (freezing) | 273.15 K |
| 68°F (room temp) | 293.15 K |
| 98.6°F (body temp) | 310.15 K |
| 212°F (boiling) | 373.15 K |
Kelvin readings are always written without a degree symbol (just "K", not "°K") -- this is a formal SI convention, since Kelvin is treated as an absolute unit rather than a relative degree scale like Fahrenheit or Celsius.
Science students converting a US-style Fahrenheit reading into Kelvin for a physics or chemistry calculation. Engineering applications that require an absolute temperature scale. For the everyday Celsius equivalent, see the Fahrenheit to Celsius Converter; for converting from Celsius directly, see the Celsius to Kelvin Converter.
A textbook problem gives a gas temperature as 77°F and asks you to apply the ideal gas law, which needs Kelvin. First convert to Celsius: (77 − 32) × 5/9 = 25°C. Then add 273.15 to reach 298.15 K. Using the Fahrenheit number directly in the gas law would give a badly wrong answer, because the formula expects a scale that starts at absolute zero.
(77 − 32) × 5/9 + 273.15 = 25 + 273.15 = 298.15 K
For 0°F, subtract 32 to get −32, multiply by 5/9 to get about −17.78°C, and add 273.15. The result is roughly 255.37 K. Notice that even a freezing-cold Fahrenheit reading is still comfortably positive in Kelvin, which is exactly why the scale is favoured in physical formulas.
Write the result as, for example, 298.15 K with no degree symbol, and keep the space between number and unit if your course or journal style asks for it. Also check how many significant figures your problem expects. If the input was given to two significant figures, quoting a result to five is false precision even though the conversion constants themselves are exact.
The result panel shows Celsius alongside Kelvin, so you can confirm the intermediate step without repeating the calculation.
First convert to Celsius by subtracting 32 and multiplying by 5/9, then add 273.15: K = (°F − 32) × 5/9 + 273.15.
0 K (absolute zero) is defined as -273.15°C, so adding 273.15 to a Celsius value shifts it onto the Kelvin scale, which has no negative numbers.
No -- Kelvin is an absolute scale starting at 0 K (absolute zero), so a physically valid Kelvin reading is never negative.
No -- Kelvin readings are written as "310 K", not "310°K", per the standard SI convention for this absolute scale.
Yes -- both the 5/9 Fahrenheit-Celsius factor and the 273.15 Celsius-Kelvin offset are exact, internationally defined constants.
(350 − 32) × 5/9 is about 176.67, and adding 273.15 gives about 449.82 K.
Only if your problem asks for it. Round according to the significant figures of your original measurement, and keep extra digits until the final step.
Many formulas need temperature to be proportional to energy, which requires a scale that starts at absolute zero. Fahrenheit has an arbitrary zero, so it must be converted.
The conversion formula is K = (°F − 32) × 5/9 + 273.15. Here are common reference temperatures converted from Fahrenheit (°F) to Kelvin (K).
| Fahrenheit (°F) | Kelvin (K) |
|---|---|
| -40 | 233.15 |
| 0 | 255.3722 |
| 32 | 273.15 |
| 50 | 283.15 |
| 68 | 293.15 |
| 77 | 298.15 |
| 98.6 | 310.15 |
| 140 | 333.15 |
| 212 | 373.15 |
| 350 | 449.8167 |
Reference: NIST Weights and Measures