Temperature Units

The most commonly used units for temperature are °Fahrenheit in the USA and °Celcius in the rest of the world. Scientific computations involving gasses are often done in Rankine or Kelvin. °Réaumur are an antique unit rarely used today included merely as a curiosity.

There's a Java Applet embedded here that computes temperature conversions amongst these units. 

Basis of temperature units

• °Fahrenheit are based on water freezing at 32° and boiling at 212°. There are 180 degrees in that interval.
• Rankine is based on the same size units as °Fahrenheit except that water freezes at 459.67 Rankine.

Temperatures in Rankine are based on the average kinetic energy of a perfect gas. Thus 0 Rankin is where molecular motion stops. This temperature has not yet been achieved on earth.

Kelvin is based on the same size units as °Celcius except that water freezes at 273.15 Kelvin.

Temperatures in Kelvin like Rankine are based on the average kinetic energy of a perfect gas. Thus 0 Kelvin is where molecular motion stops. This temperature has not yet been achieved on earth.

• °Celcius (formerly called Centigrade) are based on water freezing at 0° and boiling at 100.0°Celcius.

A more recent refinement bases the low end on the triple point of water, ice, and water vapor which is 0.01°Celcius.

• °Réaumur are based on water freezing at 0° and\nboiling at 80.0°

Formulae used in Temperature Conversions:

°Fahrenheit = 32.0 + 1.8 * °Celcius

• °Fahrenheit = 32.0 + 1.8 * (Kelvin - 273.15)
• °Fahrenheit = Rankine - 459.67
• °Fahrenheit = 32 + 2.25 * Réaumur
• °Celcius = (°Fahrenheit - 32.0) / 1.8
• Kelvin = °Celcius + 273.15
• Réaumur = °Celcius * 0.8
• Rankine = °Fahrenheit + 459.67

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