| Celsius | 25 °C |
| Fahrenheit | 77 °F |
| Kelvin | 298.15 K |
Common reference temperatures
| Reference point | Celsius | Fahrenheit | Kelvin |
|---|---|---|---|
| Absolute zero | −273.15 °C | −459.67 °F | 0 K |
| Celsius equals Fahrenheit | −40 °C | −40 °F | 233.15 K |
| Water freezes | 0 °C | 32 °F | 273.15 K |
| Room temperature | 20 °C | 68 °F | 293.15 K |
| Body temperature | 37 °C | 98.6 °F | 310.15 K |
| Water boils (sea level) | 100 °C | 212 °F | 373.15 K |
How to use the Temperature Converter
- 1Type the temperature into the Value box; negative numbers are allowed.
- 2Choose the scale you are converting from in the From list.
- 3Choose the scale you want in the To list, or press the swap button to reverse them.
- 4Read the converted temperature in the highlighted box and the same value in all three scales below it.
- 5Use the reference table for common points such as freezing, body temperature and boiling.
Temperature conversion formulas
Unlike length or weight, temperature scales do not share a common zero, so converting needs an offset as well as a multiplier. To convert Celsius to Fahrenheit, multiply by 9/5 (1.8) and add 32: °F = °C × 9/5 + 32. To convert Fahrenheit to Celsius, subtract 32 and multiply by 5/9: °C = (°F − 32) × 5/9.
Kelvin uses the same size of degree as Celsius but starts at absolute zero, so K = °C + 273.15 and °C = K − 273.15. To go between Fahrenheit and Kelvin, convert through Celsius first. Kelvin is written without a degree sign, so 300 K rather than 300 °K.
Worked examples
A warm day of 25 °C is 25 × 1.8 + 32 = 77 °F. A body temperature of 98.6 °F is (98.6 − 32) × 5/9 = 37 °C. An oven set to 350 °F is (350 − 32) × 5/9 ≈ 176.67 °C, which is why recipes usually round it to 180 °C. In science, a room-temperature sample at 300 K is 26.85 °C, or 80.33 °F.
For a rough mental conversion from Celsius to Fahrenheit, double the number and add 30. That gives 80 °F for 25 °C (the exact answer is 77 °F) and works reasonably well for everyday weather, but it becomes less accurate at very high or very low temperatures, so use the converter for anything that matters.
Absolute zero and the Kelvin scale
Absolute zero, 0 K, is the lowest temperature possible: the point at which a system has the least possible thermal energy. It equals −273.15 °C and −459.67 °F. Nothing can be colder, so the converter shows a warning if you enter a value below it. Kelvin is the SI base unit for temperature and is used throughout physics, chemistry and engineering.
One interesting point is −40, where the Celsius and Fahrenheit scales meet: −40 °C is exactly −40 °F. Our guide to metric vs imperial units explains how temperature fits alongside other everyday measurements.
Celsius and Fahrenheit around the world
Nearly every country uses Celsius for weather, cooking and medicine. The United States and a few other territories still use Fahrenheit day to day, which is why recipes, thermostats and forecasts often need converting. Heat matters for health too; in hot weather your body loses more fluid, and the water intake calculator adds extra for a hot climate.
If you are converting a recipe, you will often need weights as well. The weight converter turns ounces and pounds into grams and kilograms.
Learn more
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 1.8 and add 32. For example, 20 °C × 1.8 + 32 = 68 °F, and 100 °C × 1.8 + 32 = 212 °F.
How do I convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9. For example, (68 − 32) × 5/9 = 20 °C, and (32 − 32) × 5/9 = 0 °C, the freezing point of water.
What temperature is the same in Celsius and Fahrenheit?
−40. At that point the two scales give the same number, so −40 °C equals −40 °F, which is 233.15 K.
Can a temperature in Kelvin be negative?
No. The Kelvin scale starts at absolute zero, so 0 K is the lowest possible value. If a conversion gives a negative Kelvin result, the original temperature was below absolute zero and is not physically possible.
What is normal body temperature in Fahrenheit?
It is traditionally given as 98.6 °F, which is 37 °C. In practice, normal body temperature varies from person to person and through the day, typically within about half a degree Celsius either side. For other unit conversions, see the length converter.