Temperature Converter

Temperature measures how hot or cold something is. The Celsius scale is used by most of the world, Fahrenheit is common in the United States, and Kelvin is the scientific standard that starts at absolute zero.

Unlike most conversions, temperature scales use offset formulas rather than simple multiplication, because their zero points differ. This tool applies the correct formula for each scale automatically.

Every other converter on this site multiplies by a factor. Temperature cannot, because Celsius and Fahrenheit put their zero points in different places, so the conversion needs both a scale change and a shift, and that changes what the arithmetic means.

The practical consequence is that a temperature and a temperature difference convert differently. A reading of 10°C is 50°F, but a rise of 10°C is a rise of only 18°F. The offset applies to positions on the scale and must be left out when converting an interval.

• Kelvin shares Celsius's scale but starts at absolute zero, so K = °C + 273.15 with no multiplication. A 1°C interval and a 1 K interval are identical.
• Rankine does the same for Fahrenheit, starting at absolute zero with Fahrenheit-sized degrees.
• Because intervals convert by factor alone, they get their own converter: see the temperature interval page for differences rather than readings.

Absolute zero is the point at which a system holds no thermal energy that can be removed: 0 K, −273.15°C, or −459.67°F. It is a physical floor rather than a chosen origin, which is why Kelvin has no negative values and why scientific work uses it.

Celsius and Fahrenheit cross at exactly −40 degrees, the one reading where both scales give the same number. Above it Fahrenheit values are larger, below it smaller.

• Celsius was defined around water's freezing and boiling points at standard pressure (0 and 100), which is why those numbers are round in Celsius and not in Fahrenheit.
• Kelvin is written without a degree symbol: 300 K, not 300°K.
• Weather, cooking and body temperature are the everyday cases; anything scientific will be in kelvin.