How to Convert Kelvin to Fahrenheit

Easy Steps to Convert Back and Forth

Formula and example for converting Kelvin to Fahrenheit

ThoughtCo / Maritsa Patrinos

Kelvin and Fahrenheit are two important temperature scales. Kelvin is a standard metric scale, with a degree the same size as the Celsius degree but with its zero point at absolute zero. Fahrenheit is the temperature most commonly used in the United States. Fortunately, it's simple to convert between the two scales, providing you know the equation.

Convert Kelvin to Fahrenheit

  • The easiest formula for converting Kelvin to Fahrenheit is F = 1.8*(K-273) + 32.
  • Both Kelvin and Fahrenheit are temperature scales. However, Kelvin is an absolute scale with its zero at absolute zero. It does not have degrees. Fahrenheit is a relative scale and does have degrees.
  • Fahrenheit and Kelvin are equal at 574.25.

Kelvin to Fahrenheit Conversion Formula

Here is the formula to convert Kelvin to Fahrenheit:

° F = 9/5(K - 273) + 32

You may see the equation using more significant figures:

° F = 9/5(K - 273.15) + 32

or

° F = 1.8(K - 273) + 32

You can use whichever equation you prefer. The equation with greater precision is preferable when you have a Kelvin temperature that also has several significant digits.

It is easy to convert Kelvin to Fahrenheit with these four steps.

  1. Subtract 273.15 from your Kelvin temperature
  2. Multiply this number by 1.8 (this is the decimal value of 9/5).
  3. Add 32 to this number.

Your answer will be the temperature in degrees Fahrenheit. Remember to report this temperature in degrees.

Kelvin to Fahrenheit Conversion Example

Let's try a sample problem, converting room temperature in Kelvin to degrees Fahrenheit. Room temperature is 293K.

Start with the equation. In this example, let's use the one with fewer significant figures):

° F = 9/5(K - 273) + 32

Plug in the value for Kelvin:

F = 9/5(293 - 273) + 32

Doing the math:

F = 9/5(20) + 32
F = 36 + 32
F = 68

Fahrenheit is expressed using degrees, so the answer is that room temperature is 68° F.

Fahrenheit to Kelvin Conversion Example

Let's try the conversion the other way. For example, say you want to convert human body temperature, 98.6° F, into its Kelvin equivalent. You can use the same equation:

F = 9/5(K - 273) + 32
98.6 = 9/5(K - 273) + 32

Subtract 32 from both sides to get:
66.6 = 9/5(K - 273)

Multiply 9/5 times the values inside the parenthesis to get:
66.6 = 9/5K - 491.4

Get the variable (K) on one side of the equation. I chose to subtract (-491.4) from both sides of the equation, which is the same as adding 491.4 to 66.6:
558 = 9/5K

Multiply both sides of the equation by 5 to get:
2,790 = 9K

Finally, divide both sides of the equation by 9 to get the answer in K:
310 = K

So, human body temperature in Kelvin is 310 K. Remember, Kelvin temperature is not expressed using degrees, just a capital letter K.

Note: You could have used another form of the equation, simply rewritten to solve for the Fahrenheit to Kelvin conversion:

K = 5/9(F - 32) + 273.15

This is basically the same as saying Kelvin equals the Celsius value plus 273.15.

Remember to check your work. The only temperature where the Kelvin and Fahrenheit values will be equal is at 574.25.

More Conversions

For more conversions, see these topics:

Sources

  • Adkins, C.J. (1983). Equilibrium Thermodynamics (3rd ed.). Cambridge, UK: Cambridge University Press. ISBN 0-521-25445-0.
  • Balmer, Robert T. (2010). Modern Engineering Thermodynamics. Academic Press. ISBN 978-0-12-374996-3. 
  • Bureau International des Poids et Mesures (2006). The International System of Units (SI) Brochure (8th ed.). International Committee for Weights and Measures.
  • Grigull, Ulrich (1966). "Fahrenheit, a Pioneer of Exact Thermometry". The Proceedings of the 8th International Heat Transfer Conference. San Francisco. Vol. 1. pp. 9–18.
  • Taylor, Barry N. (2008). "Guide for the Use of the International System of Units (SI)". Special Publication 811. National Institute of Standards and Technology.
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Helmenstine, Anne Marie, Ph.D. "How to Convert Kelvin to Fahrenheit." ThoughtCo, Feb. 2, 2022, thoughtco.com/convert-kelvin-to-fahrenheit-609234. Helmenstine, Anne Marie, Ph.D. (2022, February 2). How to Convert Kelvin to Fahrenheit. Retrieved from https://www.thoughtco.com/convert-kelvin-to-fahrenheit-609234 Helmenstine, Anne Marie, Ph.D. "How to Convert Kelvin to Fahrenheit." ThoughtCo. https://www.thoughtco.com/convert-kelvin-to-fahrenheit-609234 (accessed December 2, 2022).

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