Celsius (°C)
Celsius is the temperature scale used by the vast majority of the world for everyday weather, cooking, science, and industry. Named after Swedish astronomer Anders Celsius, it defines water's freezing point as 0°C and boiling point as 100°C at standard atmospheric pressure. Outside the United States and a few other countries, virtually every weather forecast, oven dial, and medical thermometer uses degrees Celsius.
Definition
The degree Celsius is defined by the International System of Units as exactly equal in magnitude to the kelvin. The scale's zero point is set at 273.15 K, the ice point of water. This means a temperature in Celsius can be converted to kelvin by adding 273.15. One degree Celsius represents the same temperature interval as one kelvin. To convert Celsius to Fahrenheit, multiply by 9/5 and add 32. Water freezes at 0°C (32°F) and boils at 100°C (212°F) under standard atmospheric pressure of 101.325 kPa.
History
Anders Celsius proposed his temperature scale in 1742, but with an inverted arrangement: 100° for freezing and 0° for boiling. After his death in 1744, fellow Swedish scientist Carl Linnaeus (or possibly instrument maker Daniel Ekström) reversed the scale to its modern form. For over two centuries the unit was called "centigrade" because of the 100-degree interval between the freezing and boiling points of water. In 1948, the General Conference on Weights and Measures officially renamed it "degree Celsius" to avoid confusion with the centesimal gradian angle unit and to honour its inventor. Since 1954, the Celsius scale has been defined relative to the kelvin, with 0°C equal to 273.15 K.
Common Uses
Celsius is the default temperature unit in weather forecasts across Europe, Asia, Africa, South America, and Oceania. Cooking recipes in metric countries specify oven temperatures in Celsius, and food safety regulations reference Celsius for storage and cooking thresholds. Medical thermometers outside the US read in Celsius, with 37°C as normal body temperature. Scientific research universally uses Celsius or kelvin. Industrial processes, HVAC systems, and engineering specifications in metric countries are expressed in degrees Celsius.
Did You Know? Facts About Celsius
- Anders Celsius originally designed his scale backwards - water boiled at 0° and froze at 100°. The scale was reversed after his death.
- Minus 40 is the only temperature where Celsius and Fahrenheit are equal: −40°C = −40°F.
- The highest temperature ever reliably recorded on Earth was 56.7°C (134°F) at Furnace Creek, Death Valley, in 1913.
- The coldest natural temperature ever recorded was −89.2°C (−128.6°F) at Vostok Station, Antarctica, in 1983.
- The name "centigrade" was used for over 200 years before being officially changed to "Celsius" in 1948 to avoid confusion with the centesimal angle measurement.