-40 °C to °F
-40 °C equals -40 °F.
How to convert -40 °C to °F
The formula
Multiply the Celsius value by 1.8 (or 9/5), then add 32.
°F = °C × 9/5 + 32
Apply it to -40 °C
-40 × 9/5 + 32 = -72 + 32 = -40
Rounded for everyday use: -40 °F.
A quick mental estimate
For everyday weather temperatures you can double the Celsius figure and add 30: -40°C → about -50°F. The exact answer is -40°F, so the shortcut is off by 10°F here — it works best between about −10°C and 30°C and drifts at oven temperatures.
About -40 °C
-40 is the one temperature where the Celsius and Fahrenheit scales agree: -40°C and -40°F are exactly the same.
Nearby values
Convert any other value
Need a different number? Use the main Celsius to Fahrenheit converter to convert any value instantly, in either direction.
Going the other way, -40 °F converts back to -40 °C. Use the Fahrenheit to Celsius converter for any value.
Frequently asked questions
What is -40 °C in °F?
-40 °C is -40 °F.
How do you convert Celsius to Fahrenheit?
Multiply the Celsius value by 1.8 (or 9/5), then add 32. For example, -40 × 9/5 + 32 = -72 + 32 = -40.
Is -40 °C exactly -40 °F?
Yes — with the formula used on this page the result is exact.
How many °C is -40 °F?
-40 °F is -40 °C.
Why does -40 °C come up so often?
-40 is the one temperature where the Celsius and Fahrenheit scales agree: -40°C and -40°F are exactly the same.