Conversions
Temperature Converter
Enter a temperature in any scale to see it in the other two, and what a change of that size means.
The formula
°F = °C × 9/5 + 32
°C = (°F − 32) × 5/9
K = °C + 273.15
a change of 1 °C = a change of 1.8 °F (no offset)
Worked example
Body temperature, 37 °C
- 37 × 9/5 = 66.6
- 66.6 + 32 = 98.6 °F
- 37 + 273.15 = 310.15 K
Where this goes wrong
Converting a temperature change as if it were a temperature
A reading of 10 °C is 50 °F, but a rise of 10 °C is a rise of 18 °F. The +32 belongs to the scale’s zero, not to the size of a degree, so it applies to readings and never to differences. Get this wrong on a thermostat range, a tolerance or a "warmed by" figure and the error is 32 degrees. This page shows both, side by side, for exactly that reason.
Questions
- At what temperature are Celsius and Fahrenheit the same?
- At −40. It is the single point where the two scales cross, which falls out of solving °C = °C × 9/5 + 32. It is also a useful check on any conversion tool: if it does not return −40 for −40, something is wrong.
- Why does Kelvin have no degree sign?
- Because it is an absolute scale, not a scale of degrees relative to an arbitrary zero. Its zero is the coldest anything can be, so a temperature in kelvin is a quantity rather than a position on a scale. You write 310.15 K, never 310.15 °K.
- What is absolute zero in Celsius and Fahrenheit?
- −273.15 °C, or −459.67 °F. This page refuses anything colder rather than converting it, because a number below absolute zero is a typo rather than a temperature — and returning a tidy answer for it would hide the mistake.
- How do I convert Fahrenheit to Celsius in my head?
- Subtract 30 and halve it. For 70 °F that gives 20 °C against a true 21.1 — close enough to know whether to take a coat. The exact method is subtract 32, then multiply by 5/9.