Convert between Fahrenheit and Kelvin. Useful for scientific calculations, physics, and engineering.
Fahrenheit to Kelvin conversion bridges a relative scale (Fahrenheit) with an absolute scale (Kelvin). Fahrenheit uses arbitrary reference points, while Kelvin starts at absolute zero where molecular motion theoretically stops.
This conversion is common when working with US measurements in scientific contexts where absolute temperature is required for thermodynamic equations.
Important note on notation: Kelvin temperatures are written as just K (not °K). For example: 293 K (not 293°K).
Absolute zero is 0 K, which equals −273.15°C or −459.67°F.
Convert to Celsius first (subtract 32, multiply by 5/9), then add 273.15 to shift to absolute zero baseline.
Same result as Formula #1, written in a more compact form (add Rankine offset, then scale down).
Subtract 273.15 to get Celsius, then scale and shift to Fahrenheit.
Convert 68°F to Kelvin (step-by-step)
Step 1: Subtract 32 and multiply by 5/9 to get Celsius
Step 2: Add 273.15 to convert to Kelvin
| Fahrenheit | Kelvin |
|---|---|
| -459.67 °F | 0 K |
| -40 °F | 233.15 K |
| 0 °F | 255.372 K |
| 32 °F | 273.15 K |
| 50 °F | 283.15 K |
| 68 °F | 293.15 K |
| 77 °F | 298.15 K |
| 98.6 °F | 310.15 K |
| 122 °F | 323.15 K |
| 212 °F | 373.15 K |
Real phase-change points, in the Fahrenheit readings you'd actually see on a US thermometer or spec sheet, next to their Kelvin equivalents.
| Substance / event | °F | K |
|---|---|---|
| Liquid nitrogen boils | -320.44°F | 77.35 K |
| Dry ice sublimates | -109.3°F | 194.65 K |
| Mercury freezes | -37.89°F | 234.32 K |
| Water freezes | 32°F | 273.15 K |
| Ethanol boils | 173.1°F | 351.54 K |
| Water boils | 212°F | 373.15 K |
| Mercury boils | 673.9°F | 629.76 K |
| Oven's self-cleaning cycle | 900°F | 755.37 K |
Mercury's boiling point is unusually high relative to its freezing point, which is exactly why it stayed the standard thermometer fluid for so long: it's liquid across almost the entire range humans experience day to day.
They give identical results. The two-step form is easier to follow since it passes through Celsius on the way; the direct form is more compact if you already know the Fahrenheit-to-Rankine relationship.
Because Kelvin measures an absolute quantity rather than a position on an arbitrary scale, SI defines it as a plain unit, not a 'degree' offset the way Fahrenheit and Celsius are. Write 293 K, not 293°K.
Most often when a US-sourced measurement (a lab thermometer, a weather reading, an equipment spec sheet) needs to go directly into a formula that requires an absolute temperature, such as the ideal gas law, without a separate detour through Celsius first.
No. 0 K is defined as absolute zero, the coldest temperature that can physically exist, so there's nothing colder to represent with a negative number.
Around 293-298 K (68-77°F).
Related Tools
Convert Celsius to Fahrenheit.
Convert Celsius to Kelvin.
Convert Celsius to Rankine.
Convert Fahrenheit to Celsius.
Convert Fahrenheit to Rankine.
Convert Kelvin to Celsius.