How to Convert Celsius to Fahrenheit (and Back)
Updated June 2026
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Switching between Celsius and Fahrenheit takes one small formula. Here it is, both directions, plus a trick for doing it in your head.
Celsius to Fahrenheit
F = C × 9 ÷ 5 + 32
Example: 20°C = 20 × 9 ÷ 5 + 32 = 36 + 32 = 68°F.
Fahrenheit to Celsius
C = (F − 32) × 5 ÷ 9
Example: 100°F = (100 − 32) × 5 ÷ 9 = 68 × 5 ÷ 9 ≈ 37.8°C.
The mental shortcut
For a rough C→F estimate: double it and add 30. 20°C → 20×2+30 = 70 (actual 68 — close enough for weather). It drifts at extremes, so use the real formula when accuracy matters.
Reference points
| Celsius | Fahrenheit | Meaning |
|---|---|---|
| 0°C | 32°F | Water freezes |
| 37°C | 98.6°F | Body temperature |
| 100°C | 212°F | Water boils |
| -40°C | -40°F | The scales meet |
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Frequently asked questions
At what temperature are Celsius and Fahrenheit equal?
At -40°. -40°C equals -40°F — the only point where both scales read the same number.
What is a normal body temperature in Celsius?
About 37°C, which is 98.6°F. Normal ranges from roughly 36.1°C to 37.2°C.