-21 Celsius to Fahrenheit
-21°C = -5.8°F
-21 degrees Celsius is equal to -5.8 degrees Fahrenheit.
Convert -21 Celsius to Fahrenheit using our free temperature converter.
How to convert -21 °C to °F
Use the formula °F = (°C × 9/5) + 32 and substitute -21 for °C:
°F = (-21 × 9/5) + 32°F = -37.8 + 32°F = -5.8
So -21 °C = -5.8 °F.
What does -21 °C mean?
-21 °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.
- Fahrenheit
- -5.8 °F
- Kelvin
- 252.15 K
- Quick estimate (double + 30)
- -12 °F
For -21 °C the quick “double it and add 30” estimate gives -12 °F — 6.2 °F too low. The shortcut works best between about 0 °C and 20 °C; use the exact formula for anything that matters.
More in this range: Below freezing.
-21 °C and nearby values
Related conversions
The Celsius to Fahrenheit formula
°F = (°C × 9/5) + 32
Multiply the Celsius temperature by 9/5 (1.8) because a Celsius degree is 1.8 times larger than a Fahrenheit degree, then add 32 because water freezes at 32 °F rather than 0 °F. To go the other way, use °C = (°F − 32) × 5/9 — for example, -5.8 °F back to Celsius gives -21 °C.
See the formula explained in detail or the step-by-step conversion guide.
Frequently asked questions
What is -21 Celsius in Fahrenheit?
-21 degrees Celsius is equal to -5.8 degrees Fahrenheit (-21 °C = -5.8 °F).
How do you convert -21 °C to °F?
Multiply -21 by 9/5 (or 1.8) and add 32: (-21 × 1.8) + 32 = -5.8 °F.
Is -21 °C hot or cold?
It is very cold — well below freezing. -21 °C is -5.8 °F.
What is -21 °C in Kelvin?
Add 273.15 to the Celsius value: -21 °C = 252.15 K.