Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, and Rankine using the correct formulas — not a single multiplier, because temperature scales have different zero points. Values below absolute zero are rejected with a clear message.
Conversion reference
| From | To | Result |
|---|---|---|
| 0 °C | Fahrenheit (°F) | 32 °F |
| 0 °C | Kelvin (K) | 273.15 K |
| 100 °C | Fahrenheit (°F) | 212 °F |
| 100 °C | Kelvin (K) | 373.15 K |
| 37 °C | Fahrenheit (°F) | 98.6 °F |
| 37 °C | Kelvin (K) | 310.15 K |
| 98.6 °F | Celsius (°C) | 37 °C |
| 98.6 °F | Kelvin (K) | 310.15 K |
Values are generated by the converter engine, at Auto precision.
About this converter
Temperature conversion is affine, not a simple ratio: each scale has both a different degree size and a different zero. Internally the converter turns your value into kelvin (K = value × factor + offset) and then into the target scale, which keeps every pair of conversions consistent.
Because absolute zero (0 K) is the coldest possible temperature, an input that would fall below it — colder than −273.15 °C or −459.67 °F — produces a validation message rather than a number.
How to use it
- Type the temperature you want to convert in the Value field (a leading minus sign is allowed).
- Choose the scale you are converting from and the scale you want.
- Read the result; press Swap to reverse the direction or Copy result to copy it.
- If you see the absolute-zero message, check the sign and magnitude of your input.
The result updates as you type — there is no Calculate button. Use Swap to reverse the two units, and Reset to return to the defaults.
Formulas and reference points
- °F = °C × 9/5 + 32 · °C = (°F − 32) × 5/9
- K = °C + 273.15 · °C = K − 273.15
- K = (°F + 459.67) × 5/9 · °R = °F + 459.67
| Reference | °C | °F | K |
|---|---|---|---|
| Absolute zero | −273.15 | −459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Room temperature | 20 | 68 | 293.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Water boils (1 atm) | 100 | 212 | 373.15 |
FAQ
How do I convert Celsius to Fahrenheit?
Multiply the Celsius value by 9/5 and add 32. For example, 100 °C × 9/5 + 32 = 212 °F. To go the other way, subtract 32 and multiply by 5/9.
How do I convert Celsius to Kelvin?
Add 273.15. 0 °C is 273.15 K and 25 °C is 298.15 K. Kelvin has the same degree size as Celsius, just a different zero point (absolute zero).
Why do I get an "absolute zero" message?
Nothing can be colder than absolute zero: 0 K, which is −273.15 °C or −459.67 °F. If the value you entered is below that, the converter shows a message instead of a physically impossible result.
What is Rankine?
The Rankine scale is an absolute scale (its zero is absolute zero) that uses Fahrenheit-sized degrees. It is used in some US engineering contexts. 0 °F ≈ 459.67 °R.
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