How to Convert Fahrenheit to Kelvin – Formula and Examples

Do you need to convert Fahrenheit to Kelvin . The most likely reason is that someone assigned you a homework question for practice. Here is the formula for converting Fahrenheit to Kelvin. Next, two example problems show how to convert Fahrenheit to Kelvin and then Kelvin to Fahrenheit.

Fahrenheit to Kelvin Conversion Formula

There are a few different ways of writing the Fahrenheit to Kelvin conversion formula. It does not matter which one you use, so choose the one that is easiest.

• K = ⁵⁄₉(°F – 32) + 273.15
• K = ⁵⁄₉(°F + 459.67)
• K = (°F – 32)/1.8 + 273.15
• K = (°F + 459.67)/1.8

Note: some people drop the decimal from the Kelvin temperature and use “273” instead of “2713.15”. This is less precise, but usually close enough for most purposes.

How the Formula Works

The Fahrenheit to Kelvin conversion is essentially a two-step process, first converting Fahrenheit to Celsius and then Celsius to Kelvin.

The Kelvin temperature scale is an absolute temperature scale related to the Celsius temperature scale. The relationship between Kelvin and Celsius is the formula:

K = °C + 273.15

where
°C is the temperature in Celsius
K is the temperature in Kelvin.

Remember, Kelvin does not use a degree symbol (°) next to the K.

Now use the formula and convert Celsius to Fahrenheit

°C = ⁵⁄₉(°F – 32)

Put the second equation into the first equation.

K = ⁵⁄₉(°F – 32) + 273.15

This gives us a conversion factor to convert Kelvin to Fahrenheit.

Multiplying by ⁵/₉ is the same as dividing by 1.8. So, you don’t need to work with fractions.

Convert Fahrenheit to Kelvin Example Problem

Question: The average body temperature of a person is 98.6 °F. What is the average body temperature of a person in Kelvin?

Solution: Plug 96.8 into °F in the conversion factor above.

K = ⁵⁄₉(°F – 32) + 273.15

K = ⁵⁄₉(98.6 – 32) + 273.15

K = ⁵⁄₉(66.6) + 273.15

K = 37 + 273.15

K = 310.15 K

Answer: The average body temperature of a person is 310.15 Kelvin.

Kelvin to Fahrenheit Conversion Formula

To find a formula to convert Kelvin to Fahrenheit, just solve the previous equation for K. An easier method would be to use Celsius conversion factors as before. 

This time, solve the Celsius to Kelvin for K

°C = K – 273.15

Celsius is converted to Fahrenheit using the formula:

°F = ⁹⁄₅°C + 32

where °F and °C are the temperatures in Fahrenheit and Celsius respectively.

If we plug the first equation into the second equation, we get a formula to convert Kelvin to Fahrenheit.

°F = ⁹⁄₅(K – 273.15) + 32

This is the same equation you would get if you solved the Fahrenheit to Kelvin conversion for °F in the first section.

Convert Kelvin to Fahrenheit Example Problem

Question: Nitrogen is a liquid around 70 K. What is this temperature in Fahrenheit?

Solution: Plug 70 K into the conversion formula and solve for °F.

°F = ⁹⁄₅(K – 273.15) + 32

°F = ⁹⁄₅(70 – 273.15) + 32

°F = ⁹⁄₅(-203.15) + 32

°F = -365.67 + 32

°F = -333.67 °F

Answer: 70 K is the same as -333.67 °F.

For more help, try these other temperature conversion example problems:

• Convert Celsius to Fahrenheit Example Problem
• When Does Fahrenheit Equal Celsius?
• Convert Celsius to Kelvin Example Problem
• Convert Kelvin to Celsius Example Problem
• What temperature is Kelvin equal to Fahrenheit