SI Units – Temperature

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The kelvin (K) is defined by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 ×10⁻²³ when expressed in the unit J K⁻¹, which is equal to kg m² s⁻² K⁻¹, where the kilogram, meter and second are defined in terms of h, c and ∆ν_Cs. The temperature 0 K is commonly referred to as "absolute zero." On the widely used Celsius temperature scale, water freezes at 0 °C and boils at about 100 °C. One Celsius degree is an interval of 1 K, and zero degrees Celsius is 273.15 K. An interval of one Celsius degree corresponds to an interval of 1.8 Fahrenheit degrees on the Fahrenheit temperature scale.

The standard temperature at the triple point of water is provided by a special cell, an evacuated glass cylinder containing pure water. When the cell is cooled enough so that a mantle of ice forms around the reentrant well, the temperature at the interface of solid, liquid, and vapor is 273.16 K. Thermometers to be calibrated are placed in the reentrant well.

From	To Fahrenheit	To Celsius	To Kelvin
Temperature Conversion (Exact)
Fahrenheit (°F)	°F	(°F - 32) / 1.8	(°F - 32) / 1.8 + 273.15
Celsius (°C)	(°C * 1.8) + 32	°C	°C + 273.15
Kelvin (K)	(K - 273.15) * 1.8 + 32	K - 273.15	K

	Celsius (°C)	Kelvin (K)	Fahrenheit (°F)
Common Temperature Reference Points
Surface of the Sun	5600	5900	10100
Boiling Point of Water	100	373	212
Body Temperature	37	310.2	98.6
Sweltering Day	40	313	104
Hot Day	30	303	86
Room Temperature	20	293	68
Cold Day	10	283	50
Freezing Point of Water	0	273	32

Description	°F	°C
Oven Temperature Equivalencies
Cool	200	90
Very Slow	250	120
Slow	300 to 325	150 to 160
Moderately Slow	325 to 350	160 to 180
Moderate	350 to 375	180 to 190
Moderately Hot	375 to 400	190 to 200
Hot	400 to 450	200 to 230
Very Hot	450 to 500	230 to 260

Celsius Temperature Poem

30 °C is hot
20 °C is nice
10 °C is cold
0 °C is ice

Resources for Students and Teachers

Kelvin: Introduction – Temperature is one of the most important and ubiquitous measurements in human life. (NIST)
Kelvin Temperatures and Very Cold Things! (NASA)
Building a Thermometer (GLOBE Program)

League of SI Superheroes – Dr. Kelvin

This comic book-style video animation series has been developed to help middle school students learn about the 7 SI base measurement units. With the ability to speed up or slow down particles, Dr. Kelvin can measure any temperature. The kelvin temperature scale begins at absolute zero, the coldest possible temperature and the point at which even atoms would stand perfectly still.

Navigate to more SI base unit information:

Resources

Metric

Weights and Measures