Temperature Converter
Convert a temperature between Celsius, Fahrenheit, Kelvin, Rankine, Delisle, Newton, Réaumur, Rømer and Planck. Enter one value and pick its scale, then either see the equivalent on every scale at once or pick a single target scale.
Input
Output
| Unit | Value |
|---|---|
| No data yet | |
Guides
Convert any temperature between the nine scales science and history have produced: Celsius, Fahrenheit, Kelvin, Rankine, Delisle, Newton, Réaumur, Rømer and the Planck temperature. Type a value, pick the scale you have and the scale you want, and the answer appears instantly — along with the same temperature expressed on every other scale.
How to use it
- Enter the temperature in the Temperature box (negatives and decimals are fine).
- Choose the scale it is currently in under From.
- Choose the scale you want under To.
- Optionally drag Decimal places to control precision — trailing zeros are trimmed, so
212.00shows as212.
The Result field gives the converted value with its unit symbol, and the All scales table shows the same reading on all nine scales at once. Both can be copied, and the table downloads as CSV.
The formulas
Every conversion routes through Kelvin, the absolute scale:
| Scale | To Kelvin | From Kelvin |
|---|---|---|
| Celsius | K = °C + 273.15 |
°C = K − 273.15 |
| Fahrenheit | K = (°F + 459.67) × 5/9 |
°F = K × 9/5 − 459.67 |
| Rankine | K = °R × 5/9 |
°R = K × 9/5 |
| Delisle | K = 373.15 − °De × 2/3 |
°De = (373.15 − K) × 3/2 |
| Newton | K = °N × 100/33 + 273.15 |
°N = (K − 273.15) × 33/100 |
| Réaumur | K = °Ré × 5/4 + 273.15 |
°Ré = (K − 273.15) × 4/5 |
| Rømer | K = (°Rø − 7.5) × 40/21 + 273.15 |
°Rø = (K − 273.15) × 21/40 + 7.5 |
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (that is, 1.8) and add 32. So 100 °C × 1.8 = 180, + 32 = 212 °F — the boiling point of water at sea level. Going the other way, subtract 32 first, then multiply by 5/9: 98.6 °F is 37 °C, normal human body temperature.
What is absolute zero?
Absolute zero is 0 K — the point at which a system reaches its minimum possible energy. That is −273.15 °C and −459.67 °F. Nothing can be colder, which is why Kelvin and Rankine have no negative values.
What are Delisle, Newton, Réaumur and Rømer?
Historical scales, mostly obsolete but still encountered in old texts. Rømer (1701) was the first practical scale and inspired Fahrenheit. Delisle runs backwards — larger numbers mean colder, so 100 °C is 0 °De. Réaumur was widely used in 18th- and 19th-century Europe and survives in some cheese and syrup recipes. Newton was Isaac Newton's own attempt at the problem.
What is the Planck temperature?
The Planck temperature (≈ 1.417 × 10³² K) is the natural unit of temperature in Planck units — the scale at which known physics stops making predictions. Everyday temperatures are a vanishing fraction of it, so results in Tp are shown in exponential notation rather than rounding to zero.
Privacy
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