About this temperature converter
Most of the world measures temperature in Celsius, the United States uses Fahrenheit, and science uses Kelvin, which starts at absolute zero. Rankine is an absolute scale with Fahrenheit-sized degrees used in some US engineering, and Réaumur is a historical scale still found in old recipes and texts. This converter takes a temperature in any of the five and shows it in all of them at once, using the exact definitions, so 25 °C becomes 77 °F, 298.15 K, 536.67 °R, and 20 °Ré. A thermometer, a short description, and comparisons with everyday reference points help you judge how hot or cold it really is.
How to convert a temperature
- Enter the temperature. Type the number, including a minus sign or decimals if needed, or press an example.
- Choose its scale. Pick Celsius, Fahrenheit, Kelvin, Rankine, or Réaumur under Scale.
- Press Convert temperature. Read the temperature in every scale, copy any value, and check the thermometer and comparisons.
Frequently asked questions
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 (or 1.8) and add 32. For 25 °C: 25 × 1.8 = 45, plus 32 is 77 °F. To go back, subtract 32 and multiply by 5/9.
At what temperature are Celsius and Fahrenheit equal?
At −40. Minus 40 degrees Celsius is exactly minus 40 degrees Fahrenheit, which is the only point where the two scales meet.
Why does Kelvin have no degree sign?
Kelvin is an absolute scale that starts at zero energy, so its unit is simply the kelvin (K), not a degree. A change of 1 K is the same size as a change of 1 °C.
What is absolute zero?
The lowest possible temperature: 0 K, which is −273.15 °C or −459.67 °F. Nothing can be colder, so the converter rejects lower values.
Is 37 °C still normal body temperature?
It is the traditional reference value. Healthy body temperature varies between people and through the day, roughly from 36.1 °C to 37.2 °C (97 °F to 99 °F).