-40 Fahrenheit to Celsius
-40 °F = -40 °C
-40 degrees Fahrenheit equals -40 degrees Celsius.
How to convert -40 °F to °C
Use the formula °C = (°F − 32) × 5/9:
°C = (-40 − 32) × 5/9°C = -72 × 5/9°C = -40
So -40 °F = -40 °C.
Rounded values and quick estimate
- Rounded to a whole number: -40 °C
- Rounded to one decimal place: -40 °C
Quick mental estimate: subtract 30 and halve it. For -40 °F that gives about -35 °C — off by 5 °C (12.5%). Use the exact formula when precision matters.
-40 Fahrenheit in other units
−40 °F is exactly −40 °C — the only point where the Fahrenheit and Celsius scales read the same number.
This is the one temperature where the Celsius and Fahrenheit scales meet: −40 °C is exactly −40 °F. It is a handy way to remember that the two scales are not simply offset from each other.
-40 °C is very cold weather, well below the freezing point of water. It is typical of a hard winter in northern climates; warm layers, gloves and a hat are essential outdoors.
- Celsius
- -40 °C
- Degrees Réaumur
- -32 °Ré
- Degrees Delisle
- 210 °De
- Degrees Newton
- -13.2 °N
- Degrees Rømer
- -13.5 °Rø
- Kelvin
- 233.15 K
- Rankine
- 419.67 °R
-40 °F and nearby values
About fahrenheit and celsius
The Fahrenheit scale puts water’s freezing point at 32 °F and boiling point at 212 °F. It is the everyday temperature scale in the United States.
The Celsius scale sets the freezing point of water at 0 °C and its boiling point at 100 °C (at sea level). It is used for everyday temperatures in almost every country.
Related conversions
Frequently asked questions
What is -40 Fahrenheit in Celsius?
-40 degrees Fahrenheit is -40 degrees Celsius (-40 °F = -40 °C).
How do you convert -40 °F to °C?
Apply °C = (°F − 32) × 5/9: °C = (-40 − 32) × 5/9, °C = -72 × 5/9, °C = -40.
How many degrees Fahrenheit is -40 °C?
-40 °C is about -40 degrees Fahrenheit.
Why is −40 the same in °F and °C?
Solving F = 1.8C + 32 with F = C gives C = −40.