Temperature Converter

Use this free temperature converter to change a temperature between degrees Celsius, degrees Fahrenheit, kelvin and degrees Rankine. Type a number in either box and the other one follows as you type, with the same temperature in all four scales shown underneath. Pick how many decimals to round to, swap the two scales with one click, and copy a link to your conversion. Tables list the most searched temperatures from Celsius to Fahrenheit and Fahrenheit to Celsius, oven settings, key points such as freezing, boiling and absolute zero, and all 12 formulas. It is free and instant, and your numbers stay in your browser.

How to convert Celsius to Fahrenheit

Temperature scales do not start at the same point, so you cannot just multiply. You multiply and then add or subtract a fixed amount. To change Celsius to Fahrenheit, multiply by 9/5 (that is 1.8) and add 32.

For 20 °C: 20 × 1.8 = 36, and 36 + 32 = 68 °F. For 180 °C, a common baking temperature: 180 × 1.8 = 324, and 324 + 32 = 356 °F, which US recipes usually round to 350 °F.

How to convert Fahrenheit to Celsius

Go the other way: subtract 32, then multiply by 5/9.

For 72 °F: 72 − 32 = 40, and 40 × 5/9 = 22.22 °C. For 98.6 °F: 66.6 × 5/9 = 37 °C, exactly. For an oven at 350 °F the answer is 176.67 °C.

Kelvin

Kelvin is the scale used in science. One kelvin is the same size as one degree Celsius, but the scale starts at absolute zero, the lowest temperature possible. To change Celsius to kelvin, add 273.15: 25 °C is 298.15 K. To go from Fahrenheit, subtract 32, multiply by 5/9 and add 273.15: 77 °F is also 298.15 K. Kelvin does not use the word "degree" or the degree sign, and it has no negative values.

Rankine

Rankine (°R) is the Fahrenheit version of kelvin: it starts at absolute zero too, but its steps are Fahrenheit-sized. It is used in some engineering work in the United States. The rule is simple: °R = °F + 459.67. Water freezes at 491.67 °R and boils at 671.67 °R.

Absolute zero

Absolute zero is the lowest temperature possible: 0 K = −273.15 °C = −459.67 °F = 0 °R. Nothing can be colder, so the converter does not accept a temperature below it.

Why −40 is the same on both scales

Celsius and Fahrenheit meet at one point: −40 °C is exactly −40 °F. The two scales are different sizes and start in different places, so there is only one temperature where they agree.

Converting a change in temperature

A change of temperature is different from a temperature. Between freezing and boiling there are 100 Celsius degrees but 180 Fahrenheit degrees, so a change of 1 °C is a change of 1.8 °F. If the temperature rises by 10 °C, it rises by 18 °F. Use the formulas above only for actual temperatures, not for changes.

Cooking temperatures

Recipes use different scales in different countries. The oven table above lists the common settings from 140 °C to 250 °C in Fahrenheit, for example 160 °C is 320 °F, 200 °C is 392 °F and 220 °C is 428 °F. A fan (convection) oven may need about 20 °C less, so check your oven's manual.

Body temperature

Normal body temperature is usually given as 37 °C, which is 98.6 °F. A temperature of 38 °C is 100.4 °F. This converter is for everyday sums only. It is not a medical tool, so ask a doctor or pharmacist about a fever.

Which scale is used where?

• The United States uses Fahrenheit for weather and cooking, and so do a few other places, such as the Bahamas, the Cayman Islands and Palau.
• Most other countries, including the United Kingdom, Canada, Australia and those in Europe, use Celsius.
• Scientists everywhere use kelvin, or Celsius.

Common spellings

You may also see Celsius written as "celcius" and Fahrenheit as "farenheit". They are the same scales, and the converter above works the same whichever spelling you searched for. Celsius was once called centigrade, and the name was changed to Celsius in 1948.