Type a temperature in any scale – Celsius, Fahrenheit, Kelvin, Rankine and so on – and the converter shows the equivalent in the others.
Enter a value in one scale and it appears converted into all the others at once, with no formulas to remember.
Scientists and researchers often work with data from different sources that use different temperature units, and this converter simplifies the process of harmonising the data. Additionally, individuals travelling to different countries can use the temperature converter to understand the local weather conditions and adjust their clothing accordingly.
Celsius
Celsius (°C), also called centigrade, divides the range between water's freezing and boiling points into 100 degrees. It is named after the Swedish astronomer Anders Celsius, who proposed it in 1742 – with the points the other way round, boiling at 0° and freezing at 100°.
Water freezes at 0°C and boils at 100°C at standard atmospheric pressure, which makes 20°C a mild room and 37°C body temperature.
To convert Celsius to Fahrenheit, multiply by 1.8 and then add 32 to the result.
Fahrenheit
Fahrenheit is a temperature scale commonly used in the United States and a few other countries. It was developed by the German physicist Daniel Gabriel Fahrenheit in the early 18th century. The Fahrenheit scale is based on the freezing and boiling points of water, with 32 degrees Fahrenheit (°F) representing the freezing point and 212 °F representing the boiling point at standard atmospheric pressure.
The Fahrenheit scale puts 180 degrees between freezing and boiling, against 100 on Celsius, so a Fahrenheit degree is 5/9 of a Celsius degree. That makes it finer, though not more precise – that depends on the thermometer.
To convert Fahrenheit to Celsius, subtract 32 and then divide the result by 1.8.
Kelvin
Kelvin (K) is the SI unit of temperature and starts at absolute zero, -273.15°C. It is named after the Scottish physicist William Thomson, Lord Kelvin, who argued for an absolute scale in 1848.
The Kelvin scale is based on the concept of the thermodynamic temperature, which is a measure of the average kinetic energy of the particles in a substance. In this scale, the temperature is directly proportional to the amount of thermal energy possessed by the substance. The Kelvin scale is often used in scientific and engineering applications, especially in fields such as physics, chemistry, and meteorology.
Rankine
The Rankine scale is a temperature scale named after the Scottish engineer and physicist William John Macquorn Rankine. It is an absolute temperature scale that is based on the Fahrenheit scale, with zero Rankine being absolute zero. The Rankine scale is commonly used in engineering and thermodynamics, particularly in the United States.
In the Rankine scale, the size of each degree is the same as in the Fahrenheit scale, but the zero point is shifted to absolute zero. This means that the Rankine scale has the same intervals as the Fahrenheit scale, but with a different starting point. Absolute zero, which is the lowest possible temperature, is defined as 0 Rankine, equivalent to -459.67 degrees Fahrenheit.
Delisle
The Delisle scale (°De) was devised by the French astronomer Joseph-Nicolas Delisle in 1732. It runs backwards: water boils at 0°De and freezes at 150°De, so the number falls as it gets hotter.
On the Delisle scale 0°De is the boiling point of water and 150°De is the freezing point, so a rise in temperature lowers the reading. A degree Delisle is two thirds of a degree Celsius, so °C = 100 - (°De × 2/3).
Newton
Newton's definition of temperature is based on the concept of thermal expansion. According to Newton, the temperature of a substance is determined by the degree of expansion or contraction it undergoes when heated or cooled. He believed that temperature is a measure of the intensity of heat, and that it can be quantified by measuring the change in volume of a substance.
Newton's definition of temperature is closely related to his laws of motion and his understanding of the behavior of gases. He observed that when a gas is heated, its particles move faster and collide more frequently, leading to an increase in pressure and volume. Conversely, when a gas is cooled, its particles slow down, resulting in a decrease in pressure and volume.
Réaumur
Réaumur's definition of temperature is a historical measurement scale that was developed by René Antoine Ferchault de Réaumur, a French scientist, in the early 18th century. The Réaumur scale is based on the freezing and boiling points of water, with the freezing point set at 0°Ré and the boiling point at 80°Ré. This scale was widely used in Europe, particularly in France, during the 18th and 19th centuries.
Réaumur's scale was based on the concept of dividing the range between the freezing and boiling points of water into 80 equal parts, or degrees. Each degree on the Réaumur scale represented 1/80th of the temperature difference between the two reference points. This made it a relative temperature scale, as it did not directly correspond to any specific physical property of matter.
Rømer
Rømer's definition of temperature, proposed by Danish astronomer Ole Rømer in the late 17th century, was one of the earliest attempts to quantify temperature. Rømer's scale was based on the freezing and boiling points of water, similar to other temperature scales of the time. However, what set Rømer's scale apart was his choice of reference points.
Rømer defined the freezing point of water as 7.5 degrees and the boiling point as 60 degrees on his scale. This scale was based on the observation that water freezes at a temperature of approximately 7.5 degrees below the freezing point of brine, a solution of salt and water. Rømer's scale was widely used in Europe for several decades, particularly in scientific circles.