Fahrenheit and Kelvin are temperature scale units. Fahrenheit is widely used to measure temperature in the United States, while Kelvin is often used in scientific equations or calculations. You can change the temperature from Fahrenheit to Kelvin, and vice versa. There are two ways to change a quantity and, while the process is fairly simple, the second method can provide a lot more information because you can also convert a measurement to Celsius.
Step
Method 1 of 3: Converting Directly to Kelvin
Step 1. Learn the formula for changing temperature
There are two ways you can follow to convert a temperature from Fahrenheit to Kelvin, and the first method is a simple calculation that you can do to convert the quantity directly. The formula for converting Fahrenheit to Kelvin is K = (temperature quantity °F + 459.67) x 5/9.
For example, if you need to convert 75°F to Kelvin, the translation using the formula would be something like this: K = (75°F + 459, 67) x 5/9
Step 2. Add the initial quantity to 459, 67
On the Fahrenheit scale, the absolute 0 is -459.67°F. This quantity is equivalent to 0 K. Since the Kelvin scale has no negative numbers, you must first add 459.67 to Fahrenheit if you want to convert it to Kelvin.
In the previous example (75°F), the answer for the first step is 75°F + 459.67 = 534.67
Step 3. Multiply the result by 5/9 to get the temperature in Kelvin
Remember that 5/9 can be written as 0.55, with 5 being the repeating decimal. The answer to this multiplication is the temperature in Kelvin.
- In the 75°F example, the answer to step two is 5/9 x 534.67 = 297.0388, with 8 being the repeating decimal.
- The answer to the calculation (75°F + 459.67) x 5/9 is 297.0388
- Therefore, 75°F is equivalent to 297.0388 K
Method 2 of 3: Converting to Celsius First, Then to Kelvin
Step 1. Learn the formula
The second way to convert Fahrenheit to Kelvin involves first converting to Celsius. This method makes it easier for you when you have to compare the sizes of all the units of the scale. There are two formulas that can be used to convert Fahrenheit to Celsius, then to Kelvin. The first formula (1) is K = (temperature magnitude °F – 32) x 5/9 + 273, 15. Meanwhile, the second formula (2) is K = (temperature magnitude °F – 32) 1, 8 + 273, 15. Both formulas will give the same result or answer.
- For example, if you needed to convert 90°F to Kelvin using formula 1, the translation would be something like this: K = (90°F – 32) x 5/9 + 273, 15.
- For formula 2, the translation is something like this: K = (90°F – 32) 1, 8 + 273, 15.
Step 2. Reduce the initial temperature by 32
Regardless of the formula used, the first step to converting Fahrenheit to Celsius, then to Kelvin is to first subtract 32 from the initial Fahrenheit.
In the in-between example (90°F), the answer to the first step is 90°F – 32 = 58
Step 3. For formula 1, multiply the result of the subtraction by 5/9
Remember that 5/9 can also be written as 0.55. The product of this product is the temperature in Celsius.
In the 90°F example, the answer to the second step in formula 1 can be translated as follows: 58 x 0.5555 = 32, 22°C, with 2 being the repeating decimal number
Step 4. For formula 2, divide the result of subtraction by 1, 8
Dividing by 1.8 gives the same result as multiplying by 5.9. This is the temperature in Celsius.
In the 90°F example, the answer to the second step in formula 2 can be described as follows: 58 1, 8 = 32, 22 °C, with 2 being the repeating decimal number
Step 5. Add 273 to Celsius to convert it to Kelvin
The final step to follow is to add the result of the Celsius quantity to 273, 15 (this addition applies to both formulas). The result of the addition is the temperature in Kelvin. Absolute zero equals -271, 15°C or 0 K. Since the Kelvin scale has no negative numbers, you will need to add 273, 15 to the final result.
- In the 90°F example, the answer to step three could be translated as follows: 32, 22°C + 273, 15 = 305, 3722
- The answer to (90°F – 32) x 5/9 + 273, 15 or (90°F – 32) 1, 8 + 273, 15 is 305, 3722, with 2 being the repeating decimal.
- Therefore, 90°F is equivalent to 32, 22°C or 305, 3722 K
Method 3 of 3: Converting Kelvin to Fahrenheit
Step 1. Get to know the formula
To convert Kelvin to Fahrenheit, you just need to use the reciprocal of the same formula. The formula for converting Kelvin to Fahrenheit is F = temperature K x 9/5 – 459, 67.
For example, to convert 320 K to Fahrenheit, you need to use the following equation: F = 320 K x 9/5 – 459.67
Step 2. Multiply the original quantity by 9/5
Keep in mind that 9/5 can be written as 1, 8.
In the example above (320 K), the answer for the first step is 320 K x 9/5 = 576
Step 3. Subtract the product from 459, 67 to get the size in Fahrenheit
After you've multiplied the initial quantity by 9/5, subtract the product from absolute zero (-459, 67).
- In the 320 K example, the subtraction of the product can be described as follows: 576 – 459, 67 = 116, 33.
- Answer of 320 K x 9/5 – 459, 67 = 116, 33.
- Therefore, 320 K is equivalent to 116.33°F.
