Temperature Converter: Celsius, Fahrenheit, Kelvin (With Working)
Convert Celsius, Fahrenheit and Kelvin, with each step of the formula shown.
Inputs
| Unit | 25 Celsius is |
|---|---|
| Celsius | 25 |
| Fahrenheit | 77 |
| Kelvin | 298.15 |
- Factor
- No single factor: Fahrenheit and Celsius have different zero points, so the scales are offset as well as stretched
- Working
- 25 × 9/5 + 32 = 77 °F
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What each Temperature input means
- Value
- The temperature to convert. Negative values are fine down to absolute zero, −273.15 °C (−459.67 °F, 0 K).
- From
- Celsius, Fahrenheit or Kelvin. Kelvin starts at absolute zero and uses Celsius-sized degrees.
- To
- The scale you want. Because the zero points differ, the page shows the arithmetic rather than a single factor.
Temperature conversion formula
°F = °C × 9/5 + 32 · °C = (°F − 32) × 5/9 · K = °C + 273.15
Temperature scales differ in two ways at once, so no single multiplier converts them. A Fahrenheit degree is 5/9 the size of a Celsius degree, and the two scales also start from different zeros: water freezes at 0 °C and 32 °F. So to go from Celsius to Fahrenheit you stretch (× 9/5, or × 1.8) and then shift (+ 32); to come back you undo them in the reverse order — subtract 32, then × 5/9. Kelvin uses Celsius-sized degrees counted from absolute zero, so it is just °C + 273.15. The page converts through Celsius and shows each step.
Temperature conversion worked example
25 °C × 9/5 = 45, + 32 = 77 °F — a warm room. Going the other way, a body temperature of 98.6 °F is (98.6 − 32) × 5/9 = 37 °C, and in kelvin 25 °C is 298.15 K.
More Temperature examples
98.6 °F, the traditional body temperature: (98.6 − 32) × 5/9 = 37 °C.
−40 °C × 9/5 + 32 = −40 °F, shown as -40 °F: the one temperature where the two scales read the same.
Ray Bradbury's 451 °F: (451 − 32) × 5/9 = 232.777778 °C, about 233 °C.
Where the Temperature converter can give the wrong answer
- Absolute zero is −273.15 °C, −459.67 °F and 0 K. Nothing is colder, though the page will still do the arithmetic.
- A temperature difference converts without the 32: a rise of 10 °C is a rise of 18 °F.
- Kelvin is written without a degree sign: 300 K, not 300 °K.
- Results show up to six decimals, so 37 °C reads as 98.6 °F exactly.
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Temperature conversion reference table
| °C | °F | K |
|---|---|---|
| −40 | −40 | 233.15 |
| −20 | −4 | 253.15 |
| −10 | 14 | 263.15 |
| 0 | 32 | 273.15 |
| 10 | 50 | 283.15 |
| 20 | 68 | 293.15 |
| 25 | 77 | 298.15 |
| 30 | 86 | 303.15 |
| 37 | 98.6 | 310.15 |
| 40 | 104 | 313.15 |
| 100 | 212 | 373.15 |
| 180 | 356 | 453.15 |
| 200 | 392 | 473.15 |
| 220 | 428 | 493.15 |
Temperature conversion FAQ
- 32 °F — water's freezing point. 100 °C, its boiling point at sea level, is 212 °F.
- 37 °C: (98.6 − 32) × 5/9 = 66.6 × 5/9 = 37.
- −40. Setting °F = °C in °F = 1.8 × °C + 32 gives −0.8 × °C = 32, so °C = −40.
- Subtract 30 and halve it — 70 °F gives 20 °C, against the exact 21.1. It is close between about 40 and 70 °F and drifts outside that range; the page gives the exact figure.
- 356 °F. Oven dials and recipes round it to 350 °F, gas mark 4.
- Subtract 273.15: 300 K is 26.85 °C. Going the other way, add 273.15. A change of 1 K is the same size as a change of 1 °C.
- 37.8 °C: (100 − 32) × 5/9.
- 0 K, the lowest temperature possible: −273.15 °C or −459.67 °F.
- 212 °F at sea-level pressure (100 °C), and lower at altitude, where the air pressure is lower.
- 176.7 °C, which recipes and dials round to 180 °C.
- 98.6 °F: 37 × 1.8 + 32.
- 21.1 °C: (70 − 32) × 5/9.
- −0.4 °F, which is why freezers set to 0 °F and to −18 °C are the same setting in practice.
- −17.8 °C: (0 − 32) × 5/9.
- 77 °F: 25 × 1.8 + 32.
- The traditional figure is 98.6 °F, 37 °C. Healthy readings vary from person to person and through the day, so 98.6 is an average, not a target.
- 104 °F: 40 × 1.8 + 32.
- 41 °F.
- 14 °F: −10 × 1.8 + 32.
- 15.6 °C: (60 − 32) × 5/9.