Temperature converter
What is a Temperature Converter?
Temperature scales differ in both their zero point and the size of a degree, so converting between them needs a formula rather than a single factor. This converter handles the everyday scales, Celsius and Fahrenheit, the scientific absolute scales, Kelvin and Rankine, and the historical scales Delisle, Newton, Réaumur and Rømer.
How to use it
- Enter a value in any scale.
- Read the equivalent in every other scale instantly.
Key formulas
°F = °C × 9/5 + 32and°C = (°F - 32) × 5/9K = °C + 273.15°R = °F + 459.67(Rankine, the absolute Fahrenheit scale)°Ré = °C × 4/5(Réaumur)°De = (100 - °C) × 3/2(Delisle, which runs backwards)°N = °C × 33/100(Newton) and°Rø = °C × 21/40 + 7.5(Rømer)
Reference points
| Point | °C | °F | K |
|---|---|---|---|
| Absolute zero | -273.15 | -459.67 | 0 |
| Water freezes | 0 | 32 | 273.15 |
| Body temperature | 37 | 98.6 | 310.15 |
| Water boils (sea level) | 100 | 212 | 373.15 |
-40 is the one temperature where Celsius and Fahrenheit are equal.
Tips
- Kelvin is written without the degree sign: 300 K, not 300 °K.
- A temperature difference converts differently from a temperature: a change of 10 °C is a change of 18 °F, without the 32 offset.
- Quick mental estimate: double the Celsius value and add 30 to get approximate Fahrenheit.
Frequently Asked Questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32. For example, 25 °C is 77 °F.
At what temperature are Celsius and Fahrenheit equal?
At -40 degrees, which is the same in both scales.
Why is Kelvin written without a degree symbol?
Kelvin is an absolute SI unit, so it is written simply as K, for example 300 K.
What is the Rankine scale?
An absolute temperature scale that uses Fahrenheit-sized degrees, with 0 °R at absolute zero. It is still used in some US engineering fields.