Convert Celsius to Fahrenheit (2024)

Please provide values below to convert Celsius [°C] to Fahrenheit [°F], or vice versa.

Celsius

Definition: The Celsius (symbol: °C) is an SI (International System of Units) derived unit of temperature. It is defined based on the SI unit of temperature, the kelvin. The Celsius and Kelvin scales are precisely related, with a one-degree change in Celsius being equal to a one degree-change in kelvin. The kelvin (and thus Celsius) is defined based on the Boltzmann constant, k, which equals 1.380649 × 10^-23 when expressed in the unit J·K^-1, a unit equivalent to kg·m²·s^-2·K^-1. The kilogram, meter, and second, are defined based on Planck's constant, h, the speed of light, c, and cesium frequency, ΔνCs.

History/origin: From 1743 until 1954, the Celsius scale was based on 0°C for the freezing point of water and 100 °C for the boiling point of water, both at a pressure of one standard atmosphere, using mercury as the working material. This was not always the case, and originally 0°C was defined as the boiling point of water and 100°C was defined as the melting point of snow. Celsius as a unit and a scale was not widely used until this original definition was inverted. In 1954, the unit, "degree Celsius," as well as the Celsius scale were again re-defined to instead be based on absolute zero (-273.15 °C) and the triple point of VSMOW (specially purified water). This is the definition that was used up until 2019, when the kelvin was redefined based on the definitions of the second, meter, and kilogram.

Current use: The Celsius scale replaced the Fahrenheit scale in most countries in the mid to late 20^th century. Almost all countries around the world use this scale, except for those in which the metric system has not been adopted, such as the United States. Even in countries like the United States however, Celsius is widely used within the scientific community—it just is not widely used in everyday temperature references.

Fahrenheit

Definition: The Fahrenheit (symbol: °F) is a unit of temperature that was widely used prior to metrication. It is currently defined by two fixed points: the temperature at which water freezes, 32°F, and the boiling point of water, 212°F, both at sea level and standard atmospheric pressure. The interval between the freezing and boiling point is divided into 180 equal parts.

History/Origin: The Fahrenheit scale was developed based on a measurement proposed in 1724 by the German physicist Daniel Gabriel Fahrenheit. He initially based the scale on an equal ice-salt mixture, selecting the values of 30°F for the freezing point of water, and 90°F for normal body temperature. He later adjusted the scale such that the melting point of ice was 32°F and body temperature was 96°F. He chose these values to simplify the degree markings he could make on his instruments, since this difference between the temperatures allowed him to mark degree lines by bisecting the interval six times. Later, when using the freezing and boiling points of water as fixed reference points for thermometers became popular, the scale was slightly re-defined such that there would be 180 degrees separating freezing and boiling point, resulting in normal human body temperature being approximately 98°F, rather than Fahrenheit's 96°F.

Current use: Until the 1960's the Fahrenheit scale was the primary scale used in English-speaking countries. Today, most countries around the world use the Celsius temperature scale instead, many having made the change during their metrication processes (conversion to using the metric system of units). However, the Fahrenheit scale is still used as the official temperature scale in a number of countries, including the United States (as well as its unincorporated territories), the Bahamas, Belize, the Cayman Islands, and a few others.

Celsius to Fahrenheit Conversion Table

How to Convert Celsius to Fahrenheit

Example: convert 15 °C to °F:
15 °C = 15 × 9/5 + 32 = 59 °F

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