·SI-defined exact constants — formulas don't change
-40°C to °F — What is -40 Celsius in Fahrenheit?
-40°C = -40°F. Use the exact formula (°C × 9/5) + 32 to convert any Celsius temperature to Fahrenheit — algebraically exact with zero rounding, as defined by the NIST.
Answer
-40 °C = -40 °F
Exact: -40.000000 °F · uses the BIPM-defined constant
How it's calculated
(°C × 9/5) + 32 = °F
Step 1: Apply the formula to the input value.
Step 2: (-40 × 9/5) + 32 = -72 + 32 = -40
What does -40°C feel like?
-40°C is below the freezing point of water (0°C). Roads ice over and pipes freeze at sustained temperatures below 0°C. The human body begins experiencing hypothermia when core temperature drops below 35°C, and cold weather at -40°C accelerates heat loss.
-40°C in other temperature scales
Celsius
-40°C
Fahrenheit
-40°F
Kelvin
233.15 K
Common temperature references
Key temperatures from science, cooking, and medicine
| °C | °F | Reference |
|---|---|---|
| -40°C | -40°F | °C and °F are equal |
| -18°C | 0°F | Zero Fahrenheit |
| 0°C | 32°F | Water freezes |
| 10°C | 50°F | Cool day |
| 20°C | 68°F | Room temperature |
| 25°C | 77°F | Warm room |
| 37°C | 98.6°F | Body temperature |
| 38°C | 100.4°F | Fever threshold (WHO) |
| 100°C | 212°F | Water boils (sea level) |
| 160°C | 320°F | Low oven |
| 180°C | 356°F | Moderate oven (Gas Mark 4) |
| 200°C | 392°F | Hot oven (Gas Mark 6) |
| 220°C | 428°F | Very hot oven (Gas Mark 7) |
| 250°C | 482°F | Max home oven |
Celsius to Fahrenheit — Nearby Values
Click any row to open its full conversion page
| Celsius (°C) | Fahrenheit (°F) |
|---|---|
| -40 °Cthis page | -40 °F |
| -30 °C | -22 °F |
Common questions about -40 °C to °F
What is -40°C in Fahrenheit?
-40 degrees Celsius equals exactly -40 degrees Fahrenheit. The formula is (-40 × 9/5) + 32 = -40°F. In Kelvin, this is 233.15 K.
How do you convert -40°C to °F step by step?
Step 1: Multiply -40 by 9/5 (or 1.8) to get -72. Step 2: Add 32. Result: -72 + 32 = -40°F. This formula is algebraically exact — zero rounding at any step.
Is -40°C hot or cold?
-40°C is extremely cold — well below freezing, typical of polar winters.
What is -40°F back in Celsius?
-40°F converts back to exactly -40°C — which is -40°C. The conversion is perfectly reversible using the inverse formula: (°F − 32) × 5/9.
What should I wear at -40°C?
At -40°C, wear a heavy insulated parka, thermal layers, insulated boots, thick gloves, and a balaclava. Exposed skin risks frostbite in minutes. Limit outdoor time.
Related Celsius to Fahrenheit Conversions
Live calculator
Type any value — converts instantly
Fahrenheit
-40 °C=-40 °F
Formula used
(°C × 9/5) + 32 = °F
Algebraically exact — zero rounding in the formula