Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin and Rankine: each scale starts somewhere else, so the zero is shifted before scaling.
Runs entirely in your browser. Nothing is uploaded, logged or stored.
20 °C
68 °F
Fahrenheit
In every unit
| Unit | Symbol | Value |
|---|---|---|
| Celsius | °C | 20 |
| Fahrenheit | °F | 68 |
| Kelvin | K | 293.15 |
| Rankine | °R | 527.67 |
Temperature is the odd one out among conversions. Every other unit is a simple multiplication, but these scales start in different places as well as counting in different steps, so a conversion has to shift the zero before it scales.
How it works
Fahrenheit puts freezing at 32 and counts in degrees that are five ninths the size of a Celsius degree, so the conversion subtracts 32 before scaling rather than after. Kelvin uses Celsius-sized degrees starting at absolute zero, which is why it is a simple shift of 273.15.
Rankine is to Fahrenheit what Kelvin is to Celsius: the same degree size, counted from absolute zero. It survives in some engineering work and almost nowhere else.
Examples
| Case | Input | Result |
|---|---|---|
| Water freezes | 0 °C | 32 °F |
| Water boils | 100 °C | 212 °F |
| The scales cross | -40 °C | -40 °F |
Frequently asked questions
Why is twice 10 °C not 20 °C worth of heat?
Because Celsius and Fahrenheit have arbitrary zeros, so ratios on them mean nothing: 10 °C is 50 °F and 20 °C is 68 °F, not 100 °F. Only Kelvin and Rankine start at absolute zero, and only on those does "twice as hot" have a physical meaning.
Is there a temperature that reads the same on both scales?
Yes, exactly one: -40. Celsius and Fahrenheit cross there, which is why -40 needs no unit to be unambiguous.
Can I go below absolute zero?
The arithmetic will happily convert -300 °C for you. Physics will not: absolute zero is -273.15 °C, and nothing colder exists. The tool does not stop you, because it is a converter and not a physicist.
Good to know
- Every factor used here is an exact definition rather than a rounded measurement, so the only error in a result is the one that comes from displaying it with a finite number of digits.
- Because these scales have different zeros, a difference in temperature converts differently from a temperature. A rise of 10 °C is a rise of 18 °F, not of 50 °F.