How this calculator works
Both kelvin and Fahrenheit count from an absolute zero, but their degrees are different sizes. A Fahrenheit degree is 5/9 of a kelvin, so the conversion multiplies by 9/5 and then shifts the zero by 459.67 degrees. Kelvin is the SI base unit and is common in physics and astronomy, while Fahrenheit remains the everyday scale in the United States. The two lists of units let you convert in either direction.
Formula
°F = K x 9/5 - 459.67. K = (°F + 459.67) x 5/9. The 459.67 offset comes from absolute zero, which is -459.67 °F.
Worked example
273.15 K to Fahrenheit: 273.15 x 1.8 - 459.67 = 32 °F. 300 K is 80.33 °F. 310.15 K is 98.6 °F, normal body temperature. 0 K is -459.67 °F.
Advertisement
Frequently asked questions
Why is absolute zero -459.67 °F?
The Fahrenheit scale was fixed using two reference points, and the resulting degree size leaves absolute zero at -459.67 °F. The value follows from the 9/5 ratio between Fahrenheit and Celsius degrees and the 32 °F freezing point.
How is Fahrenheit related to the Rankine scale?
Rankine uses Fahrenheit-sized degrees but starts at absolute zero, so °R = °F + 459.67. Kelvin and Rankine therefore differ only by the 9/5 ratio of their degree sizes.
What is a quick mental estimate?
Double the kelvin value and subtract 460. For 300 K that gives 140 °F against the exact 80.33 °F, so the estimate is only rough because the correct slope is 1.8, not 2.
Can I enter a temperature below absolute zero?
No. Values below 0 K or -459.67 °F are rejected because they describe a state colder than absolute zero.