21°C in Fahrenheit
The exact conversion, the formula, and a mental shortcut that is close enough for weather.
The formula
Multiply by 9/5 and add 32.
(21 × 9 ÷ 5) + 32 = 37.8 + 32 = 69.8 °F
For weather, a shortcut that needs no calculator is to double the Celsius and add 30: 21 × 2 + 30 = 72, against an exact 69.8. It drifts by about 2 °F per 10 °C, which is fine for deciding what to wear and useless for cooking.
What this temperature feels like
Comfortable room temperature. Most thermostats sit in this band.
Nearby temperatures
| Celsius | Fahrenheit | Kelvin |
|---|---|---|
| 16 °C | 60.8 °F | 289.15 K |
| 17 °C | 62.6 °F | 290.15 K |
| 18 °C | 64.4 °F | 291.15 K |
| 19 °C | 66.2 °F | 292.15 K |
| 20 °C | 68 °F | 293.15 K |
| 22 °C | 71.6 °F | 295.15 K |
| 23 °C | 73.4 °F | 296.15 K |
| 24 °C | 75.2 °F | 297.15 K |
| 25 °C | 77 °F | 298.15 K |
| 26 °C | 78.8 °F | 299.15 K |
Frequently asked questions
What is 21°C in Fahrenheit?
69.8°F. Multiply the Celsius figure by 9/5 and add 32.
What is the formula?
°F = (°C × 9/5) + 32. To go the other way, °C = (°F − 32) × 5/9.
At what temperature are the two scales equal?
−40. That is the single point where Celsius and Fahrenheit give the same number, which makes it a handy check on any conversion you do by hand.
Nearby values
Last reviewed September 5, 2026.