Temperature Converter

Multiply the Celsius by 9/5 (that's 1.8) and add 32. So 20 °C is 20 × 1.8 + 32 = 68 °F, and 37 °C is 98.6 °F. A rough shortcut is to double the Celsius and add 30, which gets you close for a quick guess. This temperature converter uses the exact formula, and you'll see the result the moment you type.

Subtract 32 first, then multiply by 5/9. So 98.6 °F becomes (98.6 − 32) × 5/9 = 37 °C, and 212 °F is 100 °C. The order matters: subtract before you multiply. If you just want a ballpark, subtract 30 and halve it. Switch the From unit to Fahrenheit above and you'll read the Celsius straight away.

37 °C is 98.6 °F, the textbook normal body temperature. It comes from 37 × 1.8 + 32. A reading of 38 °C is 100.4 °F, the usual fever threshold, and 39 °C is 102.2 °F. Those few degrees Celsius cover the whole range from normal to a real fever, and that's why precision matters with body temperature.

Kelvin is the scientific scale that starts at absolute zero, the coldest possible temperature. It uses the same size degree as Celsius, so you convert by adding 273.15: 0 °C is 273.15 K and 100 °C is 373.15 K. There are no negative kelvins, and scientists drop the degree symbol, writing 300 K rather than 300°. The converter includes it alongside Rankine.

It's the one point where the two scales cross. The Fahrenheit formula multiplies by 1.8 and adds 32, and at −40 those effects cancel out exactly, so −40 °C equals −40 °F. It's a handy fact to remember, and a quick way to sanity-check that a converter is working correctly.

For Celsius to Fahrenheit, double it and add 30: 20 °C doubles to 40, plus 30 is 70, close to the true 68 °F. For Fahrenheit to Celsius, subtract 30 and halve it. These shortcuts are off by a few degrees but they're fine for weather. When you need the exact figure, the converter above has it.