Why is there no degree symbol with Kelvin?

Because the SI base unit for temperature is named kelvin and its symbol is a capital K, the unit is written without the degree sign.

Think of kelvin like the proper name of a measurement, just like meter or kilogram, so you do not add the little circle you use with degrees for Celsius or Fahrenheit; kelvin counts from absolute zero, so saying “twenty eight kelvin” is correct and you write it as “twenty eight K.” If you taught a friend who is in fifth grade, you could say that degrees are a decoration we use with temperature scales based on how people feel, like Celsius and Fahrenheit, but kelvin is a scientific scale that starts where all particle motion stops, so it uses the name itself as the unit. The reason the symbol is a single capital letter is because the International System of Units gave kelvin that rule, and scientists follow it so everyone understands the same thing. Writing a degree sign with kelvin would be mixing styles and could cause confusion in science and engineering, so the small circle is left out.

Students often write “degrees kelvin” or place a degree sign before the K because they are used to saying “degrees” with temperature, and the quick fix is to practice saying and writing “kelvin” as the unit name and “K” as the symbol. Another mistake is capitalizing the word kelvin in running text; the rule is that the unit name is lowercase but the symbol is a capital letter, so write “kelvin” but “K” for the symbol, and remembering that difference helps a lot. Some people also forget that kelvin measures from absolute zero, so reminding yourself that kelvin starts where particle motion stops makes it easier to remember why it is treated differently.

Check out www.gumballdegree.com for more videos and resources that explain temperature units and common confusions.

Why Kelvin Uses No Degree Symbol

1. Do not use degree sign
2. Treat kelvin as unit name
3. Write “K” as symbol
4. Kelvin starts at absolute zero
5. Avoid mixing unit styles

Kelvin: Why No Degree Symbol

1. Writing “degrees kelvin” with a degree sign
2. Capitalizing the unit name “Kelvin” incorrectly
3. Forgetting kelvin starts at absolute zero

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