Numbers
Spell Out | Use Numerals | Series of Numbers | Large Numbers
Numbers as Modifiers | Plural/Possessive&Numbers
In general, spell out all numbers under 11. Use numerals for most numbers 11 and above. Never follow a spelled-out number with the numeral in parentheses.
USE: five
NOT: five (5)
When to Spell Out Numbers (in Text)
Spell out the following:
- All numbers that begin a
sentence or title (or reword the phrase).
Thirty days after final test...
- Fractions without a whole
number.
two-thirds, one-fourth
- The first number when two
sets of numbers are used as separate modifiers.
fifteen 25 mm rods
When to Use Numerals
Use numerals for
- Units of measure, time,
money, or percentages.
0.25 micron, 7 cubic centimeters, 4-week average, > 90% removal efficiency
- Figures and tables. Figure
and table captions use arabic numbers. Within figures and tables,
always use numerals.
Figure 19
Table 5
- Fractions with whole numbers.
is 1 1/2 times the... - All numbers with decimals.
5.21 meters
Exceptions
Series of Numbers
Numbers listed in a series should be treated alike, whether in a paragraph, a list, or a sentence. For example, if numbers under 11 occur in a series with larger numbers, use numerals for all.
The monitor wafers were located in every fifth slot (i.e., 1, 6, 11, 16, and 21).
Large Numbers
Use capital letters (K for thousands, M for millions, B for billions) for numbers with multiple zeroes.
Long numbers may be denoted by powers of ten.
For whole numbers larger than four digits, a comma typically separates each group of three digits.
50,000
5000
1,753,856
4750.52783
When a tabular column uses commas within large numbers, retain the comma or space as a placeholder within four-digit numbers, as well.
Numbers as Modifiers
Use a hyphen between a number and its qualifier when they appear directly before a noun.
75-page report
ten-gallon capacity
Plural/Possessive Numbers
Do not use an apostrophe to make a number plural. Do use an apostrophe to make a number possessive.
in the early 1960s
one's complement
1997's budget
Use ~ for approximately.