Convert -21°C to Fahrenheit
Temperature converter
-21°C equals
-5.8°F
Freezing: Below the freezing point of water
How to convert -21°C to °F
Follow these steps to check the answer yourself.
- 1
Write the conversion formula
To convert Celsius to Fahrenheit, multiply by 9/5 and add 32.
°F = (°C × 9/5) + 32
- 2
Substitute the Celsius value
Replace °C with -21.
°F = ((-21) × 9/5) + 32
- 3
Multiply by 9/5
Work out the bracket first.
(-21) × 9/5 = -37.8
- 4
Add 32
Add the 32° offset to get Fahrenheit.
-37.8 + 32 = -5.8
Answer: -21°C = -5.8°F
-21°C and nearby temperatures
Celsius values from -26°C to -16°C converted to Fahrenheit and Kelvin. Select a value to open its own conversion page.
| Celsius | Fahrenheit | Kelvin |
|---|---|---|
| -26°C to °F | -14.8°F | 247.15 K |
| -25°C to °F | -13°F | 248.15 K |
| -24°C to °F | -11.2°F | 249.15 K |
| -23°C to °F | -9.4°F | 250.15 K |
| -22°C to °F | -7.6°F | 251.15 K |
| -21°C (this page) | -5.8°F | 252.15 K |
| -20°C to °F | -4°F | 253.15 K |
| -19°C to °F | -2.2°F | 254.15 K |
| -18°C to °F | -0.4°F | 255.15 K |
| -17°C to °F | 1.4°F | 256.15 K |
| -16°C to °F | 3.2°F | 257.15 K |
Celsius to Fahrenheit conversion chart
Common temperatures from -40°C to 200°C. Bookmark or print this chart for quick reference.
| °C | °F |
|---|---|
| -40°C | -40°F |
| -30°C | -22°F |
| -20°C | -4°F |
| -10°C | 14°F |
| -5°C | 23°F |
| 0°C | 32°F |
| 5°C | 41°F |
| 10°C | 50°F |
| °C | °F |
|---|---|
| 15°C | 59°F |
| 20°C | 68°F |
| 25°C | 77°F |
| 30°C | 86°F |
| 35°C | 95°F |
| 37°C | 98.6°F |
| 40°C | 104°F |
| 45°C | 113°F |
| °C | °F |
|---|---|
| 50°C | 122°F |
| 60°C | 140°F |
| 70°C | 158°F |
| 80°C | 176°F |
| 90°C | 194°F |
| 100°C | 212°F |
| 150°C | 302°F |
| 200°C | 392°F |
Is -21°C hot or cold?
-21°C (-5.8°F) reads as freezing on the thermometer: below the freezing point of water. Typical context: extreme cold, polar and deep-freeze conditions.
-21°C is 19°C warmer than the point where the Celsius and Fahrenheit scales meet (-40°C), and 3°C cooler than a standard home freezer (-18°C).
Quick mental math
To estimate Celsius to Fahrenheit in your head, double the Celsius value and add 30.
(-21) × 2 + 30 = -12°F (exact answer: -5.8°F)
The shortcut is close for everyday temperatures but drifts further from the exact answer in very hot or very cold conditions.
To go the other way, use the Fahrenheit to Celsius converter: -5.8°F converts back to -21°C.
Frequently asked questions
What is -21°C in Fahrenheit?
-21°C equals -5.8°F. This is calculated with the standard Celsius to Fahrenheit formula.
How do I convert -21 Celsius to Fahrenheit?
To convert Celsius to Fahrenheit, multiply by 9/5 (or 1.8) and add 32. For -21°C the result is -5.8°F.
Is -21°C hot or cold?
-21°C is very cold - well below freezing. This is severe winter weather temperature.
What is the formula for Celsius to Fahrenheit conversion?
The formula is: °F = (°C × 9/5) + 32
Good to know
- Anders Celsius proposed his scale in 1742. It was originally inverted, with 0 for boiling water and 100 for freezing; the order was flipped soon after his death.
- Daniel Gabriel Fahrenheit introduced his scale in 1724. The United States and a handful of other countries still use it for everyday temperatures.
- -40 is the only temperature that reads the same in Celsius and Fahrenheit.
- A change of 1°C or 1 K equals a change of 1.8°F.
Sources
- SI Units – Temperature (NIST (US National Institute of Standards and Technology))
Conversion formulas between °C, °F and K, and the 273.15 offset.
Written and checked by Abdul Manan.
Last updated . Results are for general information; see the disclaimer.