How to use
- Enter a temperature and choose the unit you are converting from and to. Type a minus sign for values below zero, e.g.
-10. - The formula used is shown under the result, and all four scales are listed below it.
- The arrow button swaps the two units.
Formulas
Unlike length or weight, temperature scales have different zero points, so conversion needs an offset as well as a multiplier.
| Conversion | Formula |
|---|---|
| Celsius → Fahrenheit | °F = °C × 9/5 + 32 |
| Fahrenheit → Celsius | °C = (°F − 32) × 5/9 |
| Celsius → Kelvin | K = °C + 273.15 |
| Fahrenheit → Rankine | °R = °F + 459.67 |
| Kelvin → Rankine | °R = K × 9/5 |
Examples
| Situation | Celsius | Fahrenheit |
|---|---|---|
| Water freezes | 0 °C | 32 °F |
| Comfortable room | 20 °C | 68 °F |
| Normal body temperature (US convention) | 37 °C | 98.6 °F |
| Moderate oven | about 176.7 °C | 350 °F |
| Water boils (1 atm) | 100 °C | 212 °F |
At −40 the Celsius and Fahrenheit readings are the same.
Things to keep in mind
- Kelvin is an absolute scale: nothing is colder than 0 K (−273.15 °C). Kelvin is written without a degree sign — 300 K, not 300 °K.
- Rankine (°R) is the absolute scale that uses Fahrenheit-sized degrees; it still appears in some US engineering work.
- A temperature difference converts without the offset: a rise of 10 °C is a rise of 18 °F (× 9/5), not 50 °F.
- For other units, see the length converter and weight converter.
FAQ
What is 100 °F in Celsius?
(100 − 32) × 5/9 ≈ 37.78 °C.
Is there a quick way to estimate Fahrenheit?
Double the Celsius value and add 30. For 20 °C that gives 70 °F; the exact answer is 68 °F. The estimate drifts further off at very high or low temperatures.
Why does the table say 36.5 °C for body temperature?
36.5 °C is the figure commonly cited in Korea and parts of Europe, while 98.6 °F (37 °C) is the traditional US figure. Actual body temperature varies by person, time of day and where it is measured.