Tucked deep within the weighty 10th edition of the AMA Manual of Style were brief entries providing guidelines for reporting measures of temperature. In sum: writers and editors reporting Celsius or Fahrenheit should (1) close up spaces between numerals, degree symbols, and temperature units and (2) repeat the degree symbol and the unit when reporting temperature ranges. For example: 37.5°C-37.9°C.
Simple? Yes—with the possible exception of closing up the space between numerals and degree symbols, as many non-AMA publications include a space between temperature values and degree symbols, and the degree symbol was 1 of only 3 exceptions to the usual AMA style rule to add a full space between an Arabic measure of quantity and the unit of measure. (The other exceptions being the percent sign and the symbols for normal and molar solutions, often closed up in other publications.)
To separate or not to separate? That was the question.
The new (and even more comprehensive) 11th edition aims to ease any resulting separation anxiety, now calling for a full space between temperature values and degree symbols. Moreover, units no longer need be repeated when a hyphen is used. For example: 37.5-37.9 °C.
The 11th edition also makes more explicit that the degree symbol is not used with Kelvin values and highlights that relative temperatures should be expressed as higher and lower rather than warmer or colder.–Phil Sefton
Happy to know of AMA’s decision to separate the quantity from the unit in expressing temperatures in Celsius. Wonder when the stylebook will get around to giving al its missing dot when writing et al.
I appreciate the information but it would be nice if, when sharing tips about 11th edition style, if you would include the specific paragraph number(s) in the 11th edition that state the “rule”. Also you specifically state that this was 1 of 3 exceptions. A parenthetical statement of what the other 2 were/are would also have been helpful.
Hi, Richard–this is a great question. This can be found Chapter 17 (Units of Measure), section 3 (Format, Style, and Punctuation), part 8 (Spacing).
Your 11th example as a space between degree in C — was this the force of old habits? 37.5-37.9 °C
Based on your 10th comment I would have expected it to be
37.5-37.9°C?
Pretty! This was a really wonderful post. Thank you for providing this information.
Personally, I think the change was a mistake. Most prescribing information retains the old style. The degree symbol (°) is more akin to a percentage sign than a measurement abbreviation in letters such as “mg” or “nmol/L”. They kept the spacing in “45° angle,” which I believe is preferable for all usage of degree symbols.