Usually a number and its unit have a space between them; for example, 100 km. The unit sign for 100 degrees Centigrade (100 °C) is written the same way but many people have never noticed that the degree sign belongs with the C, not with the number, so the space comes before the degree sign.

The NIST Guide for the Use of the International System of Units (SI), p. 16, section 7.2(a) says, “The symbol ºC for the degree Celsius is preceded by a space when one expresses the values of Celsius temperatures. Example:
t = 30.2 ºC.”

The IEEE Editorial Style Manual for Authors says on p. 21, under the heading Math, item 6:
Always use a regular space and not a thin space between numbers and units in text. In the table on p. 34, in the row beginning “degree Fahrenheit”, it says “Note that the symbols for °C, °F, and °R are comprised of two elements, written with no space between the ° and the letter that follows. The two elements that make up the complete symbol are not to be separated.”

Tip: If your style guide requires a non-breaking space instead of a normal space, use Ctrl+shift+spacebar to create the non-breaking space.

Published on: Nov 25, 2022 at 23:00

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