Celsius to Fahrenheit: Formulas, Chart and Shortcuts
November 9, 2026
Temperature conversions trip people up because they aren't a single multiplication. Celsius and Fahrenheit start from different zero points, so you have to shift as well as scale. Once you see why, the formulas are easy to remember.
The formulas
- Celsius to Fahrenheit: F = C × 9/5 + 32. Multiply by 1.8, then add 32.
- Fahrenheit to Celsius: C = (F − 32) × 5/9. Subtract 32 first, then multiply by 5/9.
- Celsius to Kelvin: K = C + 273.15.
- Kelvin to Celsius: C = K − 273.15.
For example, 25 °C × 1.8 = 45, plus 32 is 77 °F. Going back, 77 − 32 = 45, and 45 × 5/9 = 25 °C.
The Celsius to Fahrenheit converter and the Fahrenheit to Celsius converter do the arithmetic for any value.
Why 9/5 and 32?
Both scales are pinned to water. Water freezes at 0 °C and 32 °F, and boils at 100 °C and 212 °F at sea level. Between those two points Celsius counts 100 degrees and Fahrenheit counts 180. So a Fahrenheit degree is 100/180 = 5/9 of a Celsius degree, and every Celsius degree is 1.8 Fahrenheit degrees. The 32 is there because Fahrenheit's freezing point isn't zero.
Kelvin uses Celsius-sized degrees but starts at absolute zero, the coldest possible temperature: 0 K, which is −273.15 °C or −459.67 °F.
Where the scales meet: −40
There's one temperature that reads the same on both scales. Set F equal to C in the formula: C = 1.8C + 32, so −0.8C = 32 and C = −40. So −40 °C is exactly −40 °F. Above that point the Fahrenheit number is always larger; below it, the Celsius number is.
Celsius to Fahrenheit chart
| Celsius | Fahrenheit | Kelvin | What it feels like |
|---|---|---|---|
| −40 °C | −40.0 °F | 233.15 K | Both scales agree |
| −20 °C | −4.0 °F | 253.15 K | Very cold winter day |
| −10 °C | 14.0 °F | 263.15 K | Cold winter day |
| 0 °C | 32.0 °F | 273.15 K | Water freezes |
| 10 °C | 50.0 °F | 283.15 K | Cool spring day |
| 20 °C | 68.0 °F | 293.15 K | Room temperature |
| 25 °C | 77.0 °F | 298.15 K | Warm day |
| 30 °C | 86.0 °F | 303.15 K | Hot day |
| 37 °C | 98.6 °F | 310.15 K | Typical body temperature |
| 40 °C | 104.0 °F | 313.15 K | Heat wave |
| 100 °C | 212.0 °F | 373.15 K | Water boils at sea level |
| 180 °C | 356.0 °F | 453.15 K | Moderate oven |
| 200 °C | 392.0 °F | 473.15 K | Hot oven |
| 220 °C | 428.0 °F | 493.15 K | Very hot oven |
Fahrenheit to Celsius chart
| Fahrenheit | Celsius |
|---|---|
| 0 °F | −17.8 °C |
| 32 °F | 0.0 °C |
| 50 °F | 10.0 °C |
| 68 °F | 20.0 °C |
| 72 °F | 22.2 °C |
| 98.6 °F | 37.0 °C |
| 100 °F | 37.8 °C |
| 212 °F | 100.0 °C |
| 350 °F | 176.7 °C |
| 400 °F | 204.4 °C |
| 450 °F | 232.2 °C |
Oven temperatures
Recipes round oven settings, so conversions don't come out exact. 350 °F is 176.7 °C, which recipes usually write as 180 °C. 400 °F is 204.4 °C, usually written as 200 °C. A few degrees either way makes little difference to most baking, and home ovens are rarely that precise anyway. If your oven has a fan, many recipes suggest setting it about 20 °C lower.
A shortcut you can do in your head
Celsius to Fahrenheit: double it and add 30. 20 °C becomes 70 °F, against an exact 68 °F.
The shortcut multiplies by 2 instead of 1.8 and adds 30 instead of 32, so its error grows as you move away from 10 °C, where it happens to be exact:
| Celsius | Shortcut | Exact | Error |
|---|---|---|---|
| −10 °C | 10 °F | 14.0 °F | 4 °F low |
| 0 °C | 30 °F | 32.0 °F | 2 °F low |
| 10 °C | 50 °F | 50.0 °F | Exact |
| 20 °C | 70 °F | 68.0 °F | 2 °F high |
| 30 °C | 90 °F | 86.0 °F | 4 °F high |
| 100 °C | 230 °F | 212.0 °F | 18 °F high |
It's good for everyday weather and useless for cooking or a fever. Going the other way, subtract 30 and halve: 68 °F gives 19 °C, against an exact 20 °C.
Common mistakes
- Adding 32 before multiplying. For Celsius to Fahrenheit, multiply first. 25 °C is 25 × 1.8 + 32 = 77 °F, not (25 + 32) × 1.8.
- Converting a temperature change with the full formula. A rise of 10 °C is a rise of 18 °F, not 50 °F. The 32 only applies to actual temperatures, not differences. The same goes for "a 5 °C warmer summer", which is 9 °F warmer.
- Writing degrees Kelvin. Kelvin has no degree sign: it's 300 K, not 300 °K.
- Expecting water to boil at 100 °C everywhere. That's at sea level. At higher altitudes water boils at a lower temperature.
Related conversions
- All three scales at once. The temperature converter converts Celsius, Fahrenheit and Kelvin together.
- Kelvin. Use the Celsius to Kelvin converter or the Kelvin to Celsius converter for science work.
- Fahrenheit to Kelvin. The Fahrenheit to Kelvin converter skips the step through Celsius.