Which are correct: 20% or 20 % and 37°C or 37 °C?

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22nd Nov 2011

Which are correct: 20% or 20 % and 37°C or 37 °C?

Correct English language editing of percentage symbol

Answers: 20% and 37°C

Unlike most mathematical symbols, the percentage sign and degrees Celsius should always follow the number without a space.  All other mathematical symbols such as =, +, -, <, > are generally surrounded by a space (at least according to the AMA style guide); however, some journals use no spaces (P <0.05), and other use spaces on each side (P  < 0.05 ).  You can read more about this topic in our previous question on P  value formatting.

If you don’t have symbols such as °, < and > on your keyboard, then best way to insert these symbols  into a Microsoft word document is to use the Edit / Insert / Symbol menu, instead of using the font SimSum. SimSum looks fine; however, SimSum symbols will often be converted to meaningless squares if the file is converted or saved as a different version by your editor or reviewer.

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2 Responses to Which are correct: 20% or 20 % and 37°C or 37 °C?

  1. Jessica Keverne February 6, 2017 at 6:26 pm #

    According to http://www.bipm.org/en/publications/si-brochure/ you should leave a space before both!

  2. Andrea February 14, 2017 at 3:33 pm #

    Hi Jessica, Thanks for your comment!
    Indeed the BIPM doesn’t use spaces. I just checked the AMA style manual, and they use both % and the degrees symbol without spaces. In contrast, the American Chemical Society (ACS) uses the degrees symbol with a space!
    Perhaps I should write a new blog post that summaries these rules for different style guides!

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