Two Reference Points
Celsius sets water's freezing point at 0° and boiling point at 100°, giving a 100-degree span. Fahrenheit sets those same points at 32° and 212°, giving a 180-degree span. Because the zero points and the size of a degree both differ, converting between them needs both a multiplier and an offset.
The Formulas
Celsius to Fahrenheit: multiply by 9/5 and add 32 (°F = °C × 9/5 + 32). Fahrenheit to Celsius: subtract 32 and multiply by 5/9 (°C = (°F − 32) × 5/9). These are not simple multiplications — the +32 and −32 are essential.
Common Reference Points
| Context | °C | °F |
|---|---|---|
| Freezing water | 0 | 32 |
| Room temperature | 20 | 68 |
| Body temperature | 37 | 98.6 |
| Boiling water | 100 | 212 |