What are temperature scales?

The tool covers four scales. Celsius is used for weather and everyday temperatures in most of the world and in science, and Fahrenheit in the United States. Kelvin, the SI unit of temperature, and Rankine are absolute scales: they start at absolute zero, the coldest temperature possible, so they have no negative values. A kelvin is as large as a degree Celsius, and a degree Rankine as large as a degree Fahrenheit. Kelvin is written without a degree sign, as in 300 K.

Scale Water freezes Water boils Absolute zero
Celsius 0 °C 100 °C -273.15 °C
Fahrenheit 32 °F 212 °F -459.67 °F
Kelvin 273.15 K 373.15 K 0 K
Rankine 491.67 °R 671.67 °R 0 °R

Tool description

This tool converts temperatures between Celsius, Fahrenheit, Kelvin, and Rankine. Every temperature converter here works the same way, from the general Temperature Converter to the ones for a single pair, such as Celsius to Fahrenheit: it starts on the scales in its name, and the Source and Target menus switch to any of the four. Type a temperature, negative or with decimals, and the result appears as you type, ready to copy. The swap button turns the conversion around.

Formulas

  • °F = °C × 9/5 + 32
  • °C = (°F - 32) × 5/9
  • K = °C + 273.15
  • °R = °F + 459.67

For example, 25 °C is 25 × 9/5 + 32 = 77 °F, and 298.15 K.

Examples

Temperature Converted
0 °C 32 °F
20 °C 68 °F
37 °C 98.6 °F
100 °C 212 °F
180 °C 356 °F
-40 °C -40 °F
0 °F -17.7778 °C
350 °F 176.667 °C
300 K 26.85 °C

How it works

The conversion is done by convert-units, a JavaScript library for unit conversion, with the formulas above. Results between Celsius and Fahrenheit or Rankine, and between Kelvin and Fahrenheit or Rankine, are rounded to 6 significant digits: 350 °F shows as 176.667 °C. Results between Celsius and Kelvin, or between Fahrenheit and Rankine, keep 15 significant digits.

Tips

  • A change in temperature converts without the offset: a rise of 10 °C is a rise of 18 °F, not 50 °F. The tool converts temperatures, so for a difference, multiply it by 9/5 to go from Celsius to Fahrenheit, or by 5/9 to go back.