Definition: Temperature is a physical property that expresses (quantitatively) how cold or hot something is. The base unit of temperature in the International System of Units (SI) is the kelvin (K). Much of the world, however, uses the degrees Celsius (or degrees centigrade) (°C) and degrees Fahrenheit (°F) for everyday temperature measurements.
A temperature interval of 1 °C on the Celsius scale corresponds to a temperature interval of 1 K on the kelvin scale, 1.8 °F on the Fahrenheit scale and 1.8 °R on the Rankine scale.
Common temperature conversions
- FROM degrees Celsius (°C) TO degrees Fahrenheit (°F), kelvins (K), degrees Rankine (°R) and degrees Réaumur (°Re), respectively:
- [°F] = [°C] x 9/5 + 32
- [K] = [°C] + 273.15
- [°R] = ([°C] + 273.15) x 9/5
- [°Re] = [°C] x 4/5
- FROM degrees Fahrenheit (°F), kelvins (K), degrees Rankine (°R) and degrees Réaumur (°Re), respectively, TO degrees Celsius (°C):
- [°C] = ([°F] - 32) x 5/9
- [°C] = [K] - 273.15
- [°C] = ([°R] - 491.67) x 5/9
- [°C] = [°Re] x 5/4
Temperature Conversion Chart: Comparisons of various temperature scales for the most common temperature measurements
| ||Degrees Celsius||Degrees Fahrenheit||Kelvin||Degrees Rankine||Degrees Reaumur
|Absolute zero ||-273.15||-459.67||0.00||0.00||-218.52
|Ice and salt mixture temperature||-17.78||0.00||255.37||459.67||-14.22
|Freezing point of water at 1 atmosphere||0||32||273.15||491.67||0
|Room temperature ||20||68||293.15||527.67||16
|Standard human body temperature ||37||98.6||310.15||558.27||29.6
|Boiling point of water at 1 atmosphere||100||212||373.15||671.67||80
|Triple point of water  ||0.01||32.02||273.16||491.69||0.008
 - Absolute zero is the temperature at which the thermal motion of the particles ceases to exist in the classical description of thermodynamics.
 - Room temperature is a common term that denotes the temperature inside a building in which people live. The common range of temperature for the general human comfort is between 15 °C and 25 °C (59 °F and 77 °F). Room temperature is usually taken as being around 20 °C.
 - The body temperature measured on an individual can vary depending on a variety of factors. However, a healthy human body can maintain a fairly constant body temperature that is around 37 °C (98.6 °F).
 - Triple point of water is the temperature at which all three phases of water (liquid water, solid ice, and water vapour) coexist in thermodynamic equilibrium, at a partial vapour pressure of 611.73 Pa or 0.0060373 atm).