Temperature Converter
Convert between Celsius, Fahrenheit, and Kelvin temperature scales. Choose your units below for an instant result.
Popular Temperature Conversions
About Temperature Conversions
Three main temperature scales
Celsius (°C) is the everyday standard in most of the world, with water freezing at 0 °C and boiling at 100 °C at sea level. Fahrenheit (°F) is used in the United States; water freezes at 32 °F and boils at 212 °F. Kelvin (K) is the SI unit used in science — it starts at absolute zero (−273.15 °C) and has no negative values.
Converting between Celsius and Fahrenheit
The exact formula is °F = (°C × 9/5) + 32, or in reverse, °C = (°F − 32) × 5/9. A quick mental shortcut: double the Celsius value and add 30 to get an approximate Fahrenheit reading. For example, 20 °C → 40 + 30 = 70 °F (exact answer: 68 °F).
Kelvin and absolute zero
The Kelvin scale was defined by physicist William Thomson (Lord Kelvin) in 1848. Absolute zero — 0 K — is the theoretical temperature at which all molecular motion stops. It equals −273.15 °C or −459.67 °F. Kelvin is used in thermodynamics, astrophysics, and cryogenics. To convert Celsius to Kelvin, simply add 273.15.