21 °C at a glance
- Fahrenheit
- 69.8 °F
- Kelvin
- 294.15 K
- Rankine
- 529.47 °R
- Rounded
- 70 °F
- Quick estimate
- 72 °F
- As a change (Δ)
- Δ21 °C = Δ37.8 °F
How to convert 21 °C to Fahrenheit
°F = °C × 9/5 + 32
21 × 1.8 = 37.8
37.8 + 32 = 69.8 °F
21 × 1.8 = 37.8
37.8 + 32 = 69.8 °F
Multiply by 9/5 (1.8) because each Celsius degree spans 1.8 Fahrenheit degrees, then add 32 because water freezes at 32 °F rather than 0. The answer always has at most one decimal place, because multiplying a whole number by 1.8 can only leave tenths.
Estimate it in your head
Double it and add 30: 21 × 2 + 30 = 72 °F, which is 2.2 degrees high.
Careful with temperature changes: a rise of 21 °C is a rise of 37.8 °F — multiply by 1.8 but do not add 32.
21 °C: room temperature
- Thermostat. 21 °C equals 69.8 °F; the US Department of Energy suggests 20 °C (68 °F) in winter and about 25.5 °C (78 °F) in summer.
- Room temperature. Labels and recipes that say “room temperature” usually mean 20–22 °C (68–72 °F).
- Outdoors. 21 °C is pleasant spring or autumn weather.
Temperatures near 21 °C
| 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 |
| 21 °C | 69.8 °F | 294.15 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 |
Going the other way: 70 °F in Celsius is 21.11 °C.
Frequently asked questions
What is 21 °C in Fahrenheit?
21 °C is 69.8 °F: multiply by 1.8 (37.8) and add 32.
Is 21 °C hot or cold?
21 °C is comfortable — typical room temperature.
How do you convert 21 °C to Fahrenheit quickly?
Double it and add 30: 72 °F. The exact value is 69.8 °F.
What is 21 °C in Kelvin?
Add 273.15: 21 °C = 294.15 K.