Temperature Converter

Translate between Celsius, Fahrenheit, and Kelvin temperature scales.

Why use this tool?

Convert temperatures between Celsius, Fahrenheit and Kelvin. Temperature scales have different zero points, so this uses the full formula, not a simple multiplier.

How to use it

  1. Enter a temperature.
  2. Choose the scale it's in and the scale you want.
  3. Read the converted temperature, rounded to two decimals.

The formulas

Celsius and Fahrenheit use different zero points and different step sizes, so converting between them needs both a multiplication and an addition: °F = °C × 9/5 + 32, and °C = (°F − 32) × 5/9. Kelvin uses the same step size as Celsius but starts at absolute zero, so K = °C + 273.15.

Kelvin is written without the degree sign (300 K, not 300 °K) and can never be negative, because 0 K is the lowest temperature physically possible. The converter rounds results to two decimals.

Reference points worth knowing

Water freezes at 0 °C (32 °F, 273.15 K) and boils at 100 °C (212 °F, 373.15 K) at sea-level pressure. Normal body temperature is about 37 °C, or 98.6 °F. A comfortable room is around 20-22 °C, which is 68-72 °F.

−40 is the one temperature that is the same in Celsius and Fahrenheit, which makes a handy sanity check. Absolute zero is −273.15 °C or −459.67 °F.

Converting a change in temperature

A common trap is converting a temperature difference with the full formula. If the weather warms by 10 °C, that is a rise of 18 °F, not 50 °F: for differences you only apply the 9/5 factor and skip the +32. Differences in Celsius and Kelvin are identical, so a rise of 10 °C is also a rise of 10 K.

Oven settings follow the full formula: 180 °C is 356 °F (recipes usually round to 350 °F), 200 °C is 392 °F (about 400 °F) and 220 °C is 428 °F (about 425 °F).

Frequently asked questions

What is 37 °C in Fahrenheit?

37 × 9/5 + 32 = 98.6 °F, the traditional value for normal body temperature.

Is there a quick way to estimate Fahrenheit in my head?

Double the Celsius value and add 30. It's close for everyday weather (20 °C gives 70 °F versus the exact 68 °F) but drifts at extremes, so use the exact formula for cooking or science.

Why can't Kelvin be negative?

Kelvin starts at absolute zero, the point where particles have the least possible thermal energy. Nothing can be colder, so there are no negative Kelvin temperatures.