Convert Fahrenheit to kelvin (°F to K)
To convert Fahrenheit to kelvin, subtract 32 from the Fahrenheit temperature, multiply by 5/9, then add 273.15. It is needed in US engineering and HVAC work, physics homework set in Fahrenheit and scientific data that must be reported in SI units. This fahrenheit to kelvin converter works both ways: type Fahrenheit or kelvin into either box above and the other box, the worked formula and the chart below update as you type.
The degree Fahrenheit (°F) comes from the scale proposed by the physicist Daniel Gabriel Fahrenheit in 1724. Water freezes at 32 °F and boils at 212 °F, so 180 Fahrenheit degrees separate the two points. Fahrenheit remains the everyday scale in the United States and a handful of other territories, for weather, ovens and body temperature. Absolute zero is −459.67 °F, and a Fahrenheit degree is 5/9 of a kelvin.
The kelvin (K) is the SI base unit of temperature, named after Lord Kelvin (William Thomson). Its zero is absolute zero, the coldest temperature possible, and one kelvin is the same size as one degree Celsius. One kelvin is 1.8 Fahrenheit degrees in size, and 0 K is −459.67 °F. Kelvin is used in physics, chemistry, astronomy and cryogenics, and on light-bulb packaging to describe colour temperature — about 2,700 K for warm white and 6,500 K for daylight.
How to convert fahrenheit to kelvin with this tool
- Type a number into the Fahrenheit (°F) box — it starts at 68 °F as an example.
- Read the answer in the Kelvin (K) box and in the result panel, which also shows the formula with your number.
- To go the other way, type into the kelvin box and the Fahrenheit value is worked out backwards. For other units, open the temperature converter.
- Choose how many decimal places you want, or tap a quick value such as −459.67 °F, 0 °F, 32 °F.
- Press Copy result to paste the conversion into a message, spreadsheet or note.
Fahrenheit to Kelvin converter features
Converts both ways
Type in the Fahrenheit box to get kelvin, or in the kelvin box to get Fahrenheit. The other box follows instantly.
Exact factor
Calculations use K = (°F − 32) × 5/9 + 273.15, and rounding is applied only to the answer you see — choose Auto or 0–10 decimal places.
Formula with your number
The working is shown under the result, for example (68 − 32) × 5/9 + 273.15 = 293.15 K, so you can check it or copy the method.
Quick values and chart
Tap common values like −459.67 °F, 0 °F, 32 °F, or read the Fahrenheit-to-kelvin table further down this page.
Fahrenheit to Kelvin formula
The formula is K = (°F − 32) × 5/9 + 273.15. It is exact because kelvin is the Celsius scale shifted by exactly 273.15, and Celsius relates to Fahrenheit by exactly 5/9 with an offset of 32.
The reverse formula is °F = (K − 273.15) × 9/5 + 32. Three worked examples:
- Room temperature (68 °F): (68 − 32) × 5/9 + 273.15 = 293.15 K
- Freezing point of water (32 °F): (32 − 32) × 5/9 + 273.15 = 273.15 K
- Absolute zero (−459.67 °F): (−459.67 − 32) × 5/9 + 273.15 = 0 K
Fahrenheit, Rankine and kelvin
US engineers sometimes use the Rankine scale (°R), which starts at absolute zero like kelvin but uses Fahrenheit-sized degrees: °R = °F + 459.67, and K = °R × 5/9.
For example, a 68 °F room is 527.67 °R, and 68 °F = 293.15 K. Absolute zero is 0 K, 0 °R and −459.67 °F.
Fahrenheit to Kelvin quick reference
The values people look up most often, worked out with the exact factor:
- −459.67 °F = 0 K
- 0 °F = 255.37 K
- 32 °F = 273.15 K
- 68 °F = 293.15 K
Quick tip: Go through Celsius if it is easier to remember: subtract 32, multiply by 5/9, then add 273.15. For 212 °F that gives 100 °C and 373.15 K.
Related conversions: Fahrenheit to Celsius, Celsius to Kelvin and the full temperature converter.
Fahrenheit to Kelvin conversion table
Values in kelvin are rounded to 2 decimal places (more for very small numbers). For any value not listed, type it into the converter above.
| °F | K | °F | K |
|---|---|---|---|
| −459.67 | 0 | 77 | 298.15 |
| −100 | 199.82 | 80 | 299.82 |
| −40 | 233.15 | 90 | 305.37 |
| 0 | 255.37 | 98.6 | 310.15 |
| 10 | 260.93 | 100 | 310.93 |
| 20 | 266.48 | 150 | 338.71 |
| 32 | 273.15 | 200 | 366.48 |
| 40 | 277.59 | 212 | 373.15 |
| 50 | 283.15 | 300 | 422.04 |
| 60 | 288.71 | 350 | 449.82 |
| 68 | 293.15 | 400 | 477.59 |
| 70 | 294.26 | 500 | 533.15 |
| 72 | 295.37 | 1,000 | 810.93 |
Fahrenheit to Kelvin FAQ
What is 100 °F in kelvin?
100 degrees Fahrenheit is 310.93 kelvin: (100 − 32) × 5/9 + 273.15 = 310.93 K.
How do I convert fahrenheit to kelvin?
Subtract 32 from the Fahrenheit temperature, multiply by 5/9, then add 273.15. For example, (0 − 32) × 5/9 + 273.15 = 255.37 K. To convert back, subtract 273.15 from the kelvin value, multiply by 9/5, then add 32.
What is 0 K in Fahrenheit?
0 kelvin is −459.67 degrees Fahrenheit, because (0 − 273.15) × 9/5 + 32 = −459.67 °F.
What does 0 °F equal in kelvin?
What is room temperature in kelvin?
Room temperature is usually taken as 68–72 °F: 68 °F = 293.15 K and 72 °F = 295.37 K. Scientific “standard ambient” conditions use 25 °C, which is 77 °F or 298.15 K.