Free · Unit conversions

Fahrenheit, Celsius & Kelvin Temperature Conversion

Convert an absolute temperature between Fahrenheit, Celsius and kelvin with both selectors and reverse entry.

Formula & worked example
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How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

32 °F equals 0 °C and 273.15 K. The two temperature scales also meet at −40 °F = −40 °C.

Celsius = (Fahrenheit − 32) × 5/9; kelvin = Celsius + 273.15

Worked example

Enter these known values and leave the other values blank.

Temperature — first scale: 32 °F

Temperature — second scale: 0 °C

Assumptions and limitations

These are absolute temperatures, not temperature differences. Offsets of 32 and 273.15 apply to readings, not to a temperature interval.
Absolute temperature cannot be below 0 K, −273.15 °C or −459.67 °F. The captured guards operate in kelvin.
The calculation uses exact affine scale relationships; displayed precision may be rounded.

Common questions

Is a change of 10 °C equal to 50 °F?

No. A 10 °C difference is an 18 °F difference. This tool converts absolute readings and includes scale offsets.

Can I enter kelvin directly?

Yes. Select kelvin on either side and enter the absolute temperature.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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