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Fahrenheit and Celsius measure temperature on scales with different zero points and different degree sizes, so converting takes both a subtraction and a multiplication. This tool applies the formula, turning Fahrenheit into Celsius and back.
How is it calculated?
The conversion factor
Temperature needs an offset as well as a scale factor:
| Direction | Formula |
|---|---|
| °F → °C | (°F − 32) × 5/9 |
| °C → °F | (°C × 9/5) + 32 |
The two scales meet at −40°, where they read the same.
Common values
| Fahrenheit | Celsius |
|---|---|
| 32 °F | 0 °C |
| 68 °F | 20 °C |
| 98.6 °F | 37 °C |
| 212 °F | 100 °C |
Worked example
A 72 °F room is (72 − 32) × 5/9 = 22.2 °C. A 100 °F fever is (100 − 32) × 5/9 = 37.8 °C. Water freezes at 32 °F / 0 °C.
FAQ
How do I convert Fahrenheit to Celsius?+
Subtract 32, then multiply by 5/9. For example, 50 °F = (50 − 32) × 5/9 = 10 °C. A rough estimate is “subtract 30 and halve”.
How do I convert Celsius to Fahrenheit?+
Multiply by 9/5 (1.8) and add 32. So 25 °C = 25 × 1.8 + 32 = 77 °F.
Why do I subtract 32 first?+
Because the scales have different zero points: 0 °C equals 32 °F. Removing the 32-degree offset lines the scales up before applying the 5/9 size ratio.
What is 100°F in Celsius?+
100 °F is 37.8 °C — just above normal body temperature, which is why it registers as a mild fever.
At what point are °F and °C equal?+
At −40°. Minus 40 Fahrenheit equals minus 40 Celsius, the single temperature where both scales agree.