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Temperature is measured on three scales, and which one you meet depends on where you are: Celsius across most of the world, Fahrenheit in the US, and Kelvin in science. Converting between them isn't a simple multiply — each scale has a different zero point and step size — which is exactly why a converter helps.
Enter a value, pick the scales, and the result appears with all three temperatures shown at once.
How is it calculated?
The formulas
| Conversion | Formula |
|---|---|
| °C → °F | (°C × 9/5) + 32 |
| °F → °C | (°F − 32) × 5/9 |
| °C → K | °C + 273.15 |
| K → °C | K − 273.15 |
Fahrenheit and Celsius differ in both their zero point (32°F = 0°C) and their step size (a 1°C change is 1.8°F). Kelvin shares Celsius's step but starts at absolute zero (−273.15°C).
Reference points worth knowing
- Water freezes: 0°C = 32°F = 273.15 K
- Water boils: 100°C = 212°F = 373.15 K
- Body temperature: 37°C = 98.6°F
- Room temperature: ~20–22°C = 68–72°F
- The two scales meet at −40°: −40°C = −40°F
Why Kelvin has no degree sign
Kelvin is an absolute scale starting at absolute zero — the coldest possible temperature, where molecular motion stops. It's written "300 K", not "300°K", because it measures from a true zero rather than an arbitrary reference. Scientists use it because it makes gas and thermodynamic laws simple.
Where it helps
- Reading a US recipe or weather forecast in Fahrenheit
- Converting a scientific figure into Kelvin
- Setting an oven, checking a fever, or understanding a climate figure abroad
Worked example
A recipe says to bake at 25°C but your oven is in Fahrenheit. Converting: (25 × 9/5) + 32 = 45 + 32 = 77°F. The tool also shows 298.15 K for the same temperature. For a couple of familiar checks: a 37°C body temperature is (37 × 9/5) + 32 = 98.6°F — the classic "normal" reading — and water freezing at 0°C is exactly 32°F and 273.15 K. Notice the step-size difference: going from 0°C to 100°C spans only 100 degrees, but the same range is 32°F to 212°F, a span of 180 — which is why you can't just add or multiply by one number.
FAQ
How do I convert Celsius to Fahrenheit?+
Multiply by 9/5 and add 32: 25°C × 9/5 + 32 = 77°F. To go the other way, subtract 32 and multiply by 5/9. The tool does both and shows Kelvin too.
How do I convert Fahrenheit to Celsius?+
Subtract 32, then multiply by 5/9: (98.6 − 32) × 5/9 = 37°C. That's normal body temperature. Just pick the scales and enter the value.
What is Celsius in Kelvin?+
Add 273.15: 0°C = 273.15 K, 25°C = 298.15 K. Kelvin uses the same step size as Celsius but starts at absolute zero (−273.15°C).
Why is Kelvin written without a degree sign?+
Because it's an absolute scale measured from absolute zero, not from an arbitrary reference point. It's written "300 K", not "300°K" — the convention for absolute temperature scales.
At what temperature are Celsius and Fahrenheit equal?+
At −40°: −40°C equals −40°F exactly. It's the single point where the two scales cross, a handy fact for checking a conversion.
What is a normal oven temperature in each scale?+
A moderate oven of 180°C is 356°F (about 350°F in US recipes) and 453.15 K. The tool converts any baking temperature between the scales instantly.