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Fahrenheit and Kelvin are both units of measurement for temperature. Fahrenheit is often used for surface temperatures in the United States, and Kelvin is often used for scientific equations and calculations. It’s possible to convert temperatures from Fahrenheit to Kelvin, and vice versa. There are two ways that you can make the conversion, either converting directly to Kelvin, or converting to Celsius and then converting that measurement to Kelvin.
Steps
Converting Directly to Kelvin
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1Learn the formula. There are two ways that you can convert from Fahrenheit to Kelvin, and the first is a simple calculation that makes the conversion directly. The formula to use for this is K = (y °F + 459.67) x 5/9.[1]
- For example, if you needed to convert 75 °F to Kelvin, the formula would look like K = (75 °F + 459.67) x 5/9
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2Add 459.67 to your original temperature. On the Fahrenheit scale, absolute zero is -459.67 °F, which is equivalent to 0 K.[2] Because the Kelvin scale does not contain negative numbers, you must first add 459.67 to any Fahrenheit number when you want to make the conversion to Kelvin.
- In the example of converting 75 °F, the answer to the first step is 75 °F + 459.67 = 534.67
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3Multiply the sum by 5/9 to get the temperature in Kelvin. Remember that 5/9 can also be written as 0.55, where 5 is a repeating decimal. The answer to that product is your temperature in Kelvin.[3]
- In the example of 75 °F, the answer to the second step is 5/9 x 534.67 = 297.0388, where 8 is a repeating decimal
- The answer to (75 °F + 459.67) x 5/9 = 297.0388
- Therefore 75 °F = 297.0388 K
Converting to Celsius Then Kelvin
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1Learn the formulas. The second way of converting Fahrenheit to Kelvin involves calculating the temperature in Celsius first, which can be handy if you need to compare all the numbers. The formulas you can use to convert Fahrenheit to Celsius to Kelvin are: formula 1 is K = (y °F – 32) x 5/9 + 273.15; formula 2 is K = (y °F – 32) ÷ 1.8 + 273.15. Both formulas will produce the same result.[4]
- For example, if you needed to convert 90 °F to Kelvin, the formula 1 would look like K = (90 °F – 32) x 5/9 + 273.15
- The formula 2 would look like K = (90 °F – 32) ÷ 1.8 + 273.15
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2Subtract 32 from your original temperature. Regardless of the formula you use, the first step to converting Fahrenheit to Celsius to Kelvin is to subtract 32 from the original Fahrenheit temperature.[5]
- In the example of 90 °F, the answer to the first step is 90 °F – 32 = 58
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3Multiply the difference by 5/9 for formula 1. Remember that 5/9 is also written as 0.55. The answer to the product is your temperature in Celsius.
- In the example of 90 °F, the answer to the second step for formula 1 is 58 x 0.5555 = 32.22 °C, where the 2 is a repeating decimal.
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4Divide the difference by 1.8 for formula 2. Dividing by 1.8 will give you the same result as multiplying by 5/9. The quotient is your temperature in Celsius.
- In the example of 90 °F, the answer to the second step for formula 2 is 58 ÷ 1.8 = 32.22 °C, where the 2 is a repeating decimal.
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5Add 273 to the product or quotient to get your temperature in Kelvin. The final step of the conversion is adding 273.15 to the product of formula 1 or the quotient of formula 2. This gives the temperature in Kelvin. Absolute zero is equivalent to -273.15 °C and 0 K, and because the Kelvin scale doesn’t have negative numbers, you must add 273.15 to the final result.[6]
- In the example of 90 °F, the answer to the third step is 32.22 °C + 273.15 = 305.3722
- The answer to both (90 °F – 32) x 5/9 + 273.15 and (90 °F – 32) ÷ 1.8 + 273.15 = 305.3722, where 2 is a repeating decimal.
- Therefore, 90 °F = 32.22 °C = 305.3722 K
Converting Kelvin to Fahrenheit
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1Know the formula. To convert Kelvin to Fahrenheit instead, you simply use the same formula, but in reverse. The formula for converting Kelvin to Fahrenheit is F = y K x 9/5 – 459.67.[7]
- For example, to convert 320 K, you'd use the equation F = 320 K x 9/5 – 459.67
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2Multiply your original temperature by 9/5. Remember that 9/5 can also be written as 1.8.
- In the example of 320 K, the answer to step one is 320 K x 9/5 = 576.
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3Subtract 459.67 from the product to get your temperature in Fahrenheit. Once you’ve multiplied the temperature in Kelvin by 9/5, simply subtract the Fahrenheit temperature of absolute zero (-459.67) from the product.[8]
- In the example of 320 K, the answer to step two is 576 – 459.67 = 116.33
- The answer to 320 K x 9/5 – 459.67 = 116.33
- Therefore, 320 K = 116.33 °F
Community Q&A
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QuestionCan anybody make it simpler?
DonaganTop AnswererTo the Fahrenheit temperature, add 459.67°. Multiply that sum by 5, then divide that product by 9. The quotient will be expressed in "kelvins" rather than degrees. Unfortunately it doesn't get any simpler than that. Here's an example: to convert 100° Fahrenheit to kelvins, add 100 + 459.67 = 559.67. Multiply by 5: 2798.35. Divide by 9: 34.55 kelvins. -
QuestionHow do I convert Kelvin to Fahrenheit?DonaganTop AnswererMultiply the Kelvin temperature by 9/5 and subtract 459.67.
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QuestionDoes kelvin have SI units?DonaganTop AnswererYes, the kelvin is one of the units in the International System (SI) of Units.
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References
- ↑ http://www.metric-conversions.org/temperature/fahrenheit-to-kelvin.htm
- ↑ https://www.cuemath.com/fahrenheit-to-kelvin-formula/
- ↑ https://www.cuemath.com/fahrenheit-to-kelvin-formula/
- ↑ https://www.rapidtables.com/convert/temperature/celsius-to-kelvin.html
- ↑ https://www.cuemath.com/celsius-to-kelvin-formula/
- ↑ https://www.metric-conversions.org/temperature/celsius-to-kelvin.htm
- ↑ http://www.rapidtables.com/convert/temperature/how-kelvin-to-fahrenheit.htm
- ↑ https://www.rapidtables.com/convert/temperature/kelvin-to-fahrenheit.html
About This Article
The easiest way to convert from Fahrenheit to Kelvin is to use the conversion formula, K = (y° F + 459.67) x 5/9. In this formula, y equals the number of degrees Fahrenheit that you’d like to convert to Kelvin. The Kelvin scale starts at absolute 0, which is equivalent to -459.67° F. For this reason, you’ll need to start by adding 459.67 to your temperature in degrees Fahrenheit. For instance, if you’re converting 61° F to Kelvin, add 61 + 459.67 to get 520.67. Next, multiply the sum by 5/9 to complete the conversion. In our example, 520.67 x 5/9 equals approximately 289.26 K. To convert back to Fahrenheit, just reverse the process—multiply the temperature in Kelvin by 9/5, then subtract 459.67 from the product. Another method for converting from Fahrenheit to Kelvin is to convert to Celsius first, then convert the temperature in degrees Celsius to Kelvin. To go from Fahrenheit to Celsius, subtract 32 from the temperature in degrees Fahrenheit. For instance, in our example of 61° F, take away 32 to get 29° C. From there, use the formula K = y° C x 5/9 + 273.15 to convert to Kelvin. In this example, 29° C x 5/9 + 273.15 equals approximately 289.26 K. To learn how to convert a temperature from Fahrenheit to Celisus to Kelvin, scroll down!
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