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SI Units: Temperature

The Kelvin (K) is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. 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.

Temperature Conversion (Exact)
From To Fahrenheit To Celsius To Kelvin

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



Common Temperature Reference Points

  Celsius (°C) Kelvin Fahrenheit (°F)
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



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

Celsius Temperature Poem

  • 30 °C is hot
  • spring-day1024 20 °C is nice
  • fall-leaf 10 °C is cold
  • snowflake347 0 °C is ice

kelvin_front_webLeague 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.