-40 Fahrenheit to Celsius
-40 degrees Fahrenheit equals
-40°C
-40 degrees Celsius
-40°F is -40°C — deep-freeze territory, colder than a household freezer and cold enough to risk frostbite on exposed skin within minutes. -40°C is the single point where both scales agree, reading -40°F as well.
How to convert -40°F to °C
Formula
°C = (°F − 32) × 5/9
Substituting -40°F
- -40 − 32 = -72
- -72 × 5/9 = -40
Fahrenheit places the freezing point of water at 32 rather than 0, so that offset comes off first. What remains is then scaled by 5/9, because a Celsius degree covers 1.8 times as much temperature change as a Fahrenheit degree.
How -40°F compares
| Reference point | Temperature | Difference |
|---|---|---|
| Freezing point of water | 0°C / 32°F | 40°C (72°F) colder |
| Room temperature | 21°C / 69.8°F | 61°C (109.8°F) colder |
| Body temperature | 37°C / 98.6°F | 77°C (138.6°F) colder |
| Boiling point of water | 100°C / 212°F | 140°C (252°F) colder |