How this calculator works
Temperature scales differ by an offset as well as a scale factor, so this is an affine conversion rather than a single multiply. The formulas can be written with Celsius as a reference: the Fahrenheit span of 180 degrees covers the same range as 100 Celsius degrees, giving the factor 9/5, and the kelvin scale shares the Celsius degree size with its zero at absolute zero. Entries below absolute zero, exactly -273.15 °C or -459.67 °F or 0 K, are rejected because no colder temperature exists.
Formula
°F = °C × 9/5 + 32; °C = (°F - 32) × 5/9; K = °C + 273.15. All three constants are exact.
Worked example
25 °C to Fahrenheit: 25 × 9/5 + 32 = 77 °F. 98.6 °F to Celsius: (98.6 - 32) × 5/9 = 37 °C. 0 K on the Fahrenheit scale: -459.67 °F.
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Frequently asked questions
Why is there an offset and not just a factor?
The scales place zero at different points: water freezes at 0 °C but 32 °F. Any conversion has to shift the zero as well as rescale the degrees.
What is absolute zero?
Exactly -273.15 °C, -459.67 °F or 0 K. It is the lower limit of temperature, so this page rejects anything colder.
Is the kelvin written with a degree sign?
No. The kelvin is an SI base unit and is written K, while degrees Celsius and degrees Fahrenheit keep their symbols °C and °F.