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Celsius (°C)

Also called: °C, degree Celsius, centigrade

Definition: Celsius is a temperature scale in which one degree has the same size as one kelvin, with 0 °C equal to 273.15 K; water freezes near 0 °C and boils near 100 °C at standard pressure.

Updated November 3, 2026 · How we check facts

The degree Celsius (°C) is the everyday temperature unit in most countries and the unit used in science alongside the kelvin. Both have the same size, so a change of 1 °C equals a change of 1 K; only the zero point differs, with 0 °C set at 273.15 K.

Formula

°C = K − 273.15
°C = (°F − 32) ÷ 1.8
°F = °C × 1.8 + 32

Example

Body temperature of 98.6 °F is (98.6 − 32) ÷ 1.8 = 37 °C. A 25 °C room is 25 × 1.8 + 32 = 77 °F, and 25 + 273.15 = 298.15 K. Oven settings convert the same way: 180 °C is 356 °F. See the Celsius to Fahrenheit guide, the converter and Celsius to Kelvin.

Celsius vs Fahrenheit

A Fahrenheit degree is 5/9 the size of a Celsius degree, so −40 is the one temperature where both scales read the same number. See Fahrenheit.

Calculate it

Free toolCelsius to Fahrenheit Converter°C to °F and back, with the formula shown.Open →

Guides that explain it

How to Convert Celsius to Fahrenheit (Formula, Shortcut and Chart)

Related terms

Kelvin (K)The kelvin is the SI base unit of temperature. It starts at absolute zero (0 K), and one kelvin is the same size as one degree Celsius, with 0 °C equal to 273.15 K.Fahrenheit (°F)Fahrenheit is the temperature scale used for everyday weather and cooking in the United States; a degree is 5/9 the size of a Celsius degree, and 32 °F equals 0 °C.Absolute ZeroAbsolute zero is 0 K, the lowest point of the kelvin temperature scale. On the Celsius scale it equals −273.15 °C, and on the Fahrenheit scale about −459.67 °F.Greatest Common Factor (GCF)The greatest common factor (GCF) of two or more positive integers is the largest whole number that divides each of them with no remainder; it is also called the GCD or HCF.International System of Units (SI)The International System of Units (SI) is the modern metric system: seven base units, including the meter, kilogram, second and kelvin, with prefixes that scale by powers of ten.Least Common Multiple (LCM)The least common multiple (LCM) of two or more positive integers is the smallest positive number that each of them divides into evenly; it gives the lowest common denominator.Mixed NumberA mixed number combines a whole number and a proper fraction, such as 4 9/100; it equals an improper fraction, here 409/100, and is what a decimal with a nonzero whole part converts to.Percent ChangePercent change is the difference between a new and an original value, divided by the original value and expressed as a percentage; a positive result is an increase and a negative one a decrease.

Sources