How it’s calculated
Celsius and kelvin have the same degree size; Fahrenheit and Rankine degrees are 5/9 as large. The scales differ in where zero sits.
Example: 20 °C × 9/5 + 32 = 68 °F = 293.15 K.
| Reference point | °C | °F |
|---|---|---|
| Water freezes | 0 | 32 |
| Body temperature (typical) | 37 | 98.6 |
| Water boils (sea level) | 100 | 212 |
| Same on both scales | −40 | −40 |
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (1.8) and add 32. For example, 25 °C × 1.8 + 32 = 77 °F. A quick mental estimate is "double it and add 30".
How do I convert Fahrenheit to Celsius?
Subtract 32, then multiply by 5/9. For example, (350 °F − 32) × 5/9 ≈ 176.7 °C, which is why recipes give 175–180 °C for 350 °F.
At what temperature are Celsius and Fahrenheit equal?
At −40: −40 °C is exactly −40 °F.
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Sources
- SI Units – Temperature — U.S. National Institute of Standards and Technology
- NIST Guide to the SI (Special Publication 811) — U.S. National Institute of Standards and Technology
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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