Spaces in units of measurement
For most units of measurement, when you specify a number with the unit, use a nonbreaking space between the number and the unit. This guidance applies in both HTML and Markdown.
Not recommended: 64GB
However, when the unit of measure is money or percent or degrees of an angle, don't use a space. See also Currency.
For degrees of temperature, don't use a space before the degree symbol, but do use a nonbreaking space between the degree symbol and the abbreviation for the temperature scale (F or C). For Kelvin temperatures, leave out the degree symbol but use a nonbreaking space before the K.
Ranges of numbers with units
In a range of numbers, repeat the unit for each number.
Use the word to between the numbers, rather than a hyphen. A hyphen can be misinterpreted as a subtraction sign.
Not recommended: -40-85° C
Recommended: -40° C to 85° C
Using k to indicate thousands
In some contexts, it may be appropriate to indicate thousands of something by following a number with a lowercase k. If you do that, then follow these guidelines:
- Don't put a space between the number and k.
- Add a noun to indicate what the number measures, and to make clear that you're not using k as an abbreviation for kilobytes.
Recommended: On this plan, you are limited to 55k download operations and 20k upload operations per day.
If you're writing about monetary amounts, make sure the reader knows what currency you're referring to. For example, the dollar sign—the $ symbol—can refer to US dollars, Canadian dollars, Mexican pesos, and several other currencies.
If there's any possibility of ambiguity, use a currency indicator before the amount. For details, see section 9.20 and following in the Chicago Manual of Style, 17th edition.