1 °C = 33.8 °F
Temperature is the one category here that cannot be converted by multiplication alone. Each scale has both a different degree size and a different zero point, so every conversion applies an offset as well as a ratio. Celsius and Kelvin share a degree size but sit 273.15 apart; Fahrenheit and Rankine share a smaller degree and are offset by 459.67. All eight historical scales below convert through Celsius.
Formula °F = (°C × 9/5) + 32
| Celsius | Fahrenheit |
|---|---|
| -40 °C | -40 °F |
| -20 °C | -4 °F |
| -10 °C | 14 °F |
| 0 °C | 32 °F |
| 5 °C | 41 °F |
| 10 °C | 50 °F |
| 20 °C | 68 °F |
| 25 °C | 77 °F |
| 30 °C | 86 °F |
| 37 °C | 98.6 °F |
| 100 °C | 212 °F |
Celsius is used in almost every country and in science. Water freezes at 0°C and boils at 100°C at sea level, and a healthy body temperature is about 37°C. Fahrenheit, used in daily life in the United States and a few other places, puts freezing at 32°F and boiling at 212°F, so a degree is smaller: 1.8°F for every 1°C.
Kelvin is the SI scale for science and engineering. It uses Celsius-sized degrees but starts at absolute zero, so 0 K is −273.15°C and 273.15 K is the freezing point of water. Rankine is the Fahrenheit-sized equivalent, used in some US engineering work. Older scales such as Réaumur, Delisle, Newton and Rømer are mostly historical, though the converter handles them.
For quick weather conversions, remember that 0°C is 32°F, 10°C is 50°F, 20°C is 68°F and 30°C is 86°F. Each 10°C step adds 18°F. To convert to Fahrenheit in your head, double the Celsius value and add 30, which is accurate to within about 5 degrees at everyday temperatures. Use the formula when it matters, such as baking, laboratory work or medical readings.
Related guides: Imperial vs metric: differences and quick conversion tricks