Celsius vs Fahrenheit Explained
The two temperature scales, the conversion formulas and handy reference points.
Published by QuickUtilaUpdated 2 min read
Most of the world measures temperature in degrees Celsius, while the United States and a few other places use degrees Fahrenheit for everyday temperatures. The two scales measure the same thing, but they use different zero points and different sizes of degree.
How the two scales are defined
On the Celsius scale, water freezes at 0 °C and boils at 100 °C at sea level, so there are 100 degrees between the two. On the Fahrenheit scale, water freezes at 32 °F and boils at 212 °F — a gap of 180 degrees.
Because 180 ÷ 100 = 1.8, one Celsius degree is 1.8 times larger than one Fahrenheit degree. That ratio (9/5) and the 32-degree offset are all you need to convert.
Celsius to Fahrenheit
- 120 × 9/5 = 36
- 236 + 32 = 68
Therefore: 20 °C is 68 °F.
Fahrenheit to Celsius
- 1350 − 32 = 318
- 2318 × 5/9 = 176.67
Therefore: 350 °F is about 176.67 °C, usually rounded to 175 or 180 °C in recipes.
A quick mental estimate
To estimate Fahrenheit from Celsius, double the Celsius figure and add 30. For 15 °C that gives 60 °F (the exact answer is 59 °F). To go the other way, subtract 30 and halve. The estimate is closest near everyday temperatures and drifts further off at extremes.
Useful reference points
| Celsius | Fahrenheit | |
|---|---|---|
| Water freezes | 0 °C | 32 °F |
| Cool day | 10 °C | 50 °F |
| Room temperature | 20 °C | 68 °F |
| Hot summer day | 30 °C | 86 °F |
| Body temperature | 37 °C | 98.6 °F |
| Water boils | 100 °C | 212 °F |
| Both scales equal | −40 °C | −40 °F |
Where Kelvin fits in
Scientists use the Kelvin scale, which starts at absolute zero — the coldest possible temperature. A kelvin is the same size as a Celsius degree, so converting is just a matter of adding 273.15: 0 °C is 273.15 K. Kelvin temperatures are written without a degree sign.