In general, spell out numbers one through ten in non-technical usage. However, when a publication is predominantly quantitative (or highly technical), use numerals instead of words to designate all numbers except those used in a non-quantitative manner (such as “in any one year”). One and zero are problematic because of their visual similarity in numeric form to letters (that is, “1” is easily confused with “l” or “I,” and “0” with “O”), so these are almost always spelled out.
Spell out numbers if they begin a sentence, or rewrite to avoid this situation.
Always use numerals with abbreviated units (also known as unit symbols): 3 oz, 14 lb, etc.
There is no period after unit symbols. Exception: where a period is needed to distinguish the symbol from the word “in.”
Example: Space bean seeds 3 in. apart in rows that are 12 in. apart.
Unit symbols are identical for singular and plural usage (do not add an “s”).
Example: Mix 1 lb of fertilizer and 10 lb of sand.
Do not use either single or double quotation marks to stand for feet and inches; use the unit symbols: ft and in.
Use standard English units; do not include metric units as well.
In a designed publication, keep numerals and their unit symbols on the same line; do not allow a line break to separate them.
Use the percent symbol with numerals in technical publications that have many numerals and symbols; spell out “percent” otherwise. Maintain consistency on this within a single publication.