In general, use numerals to express numbers 10 and above, and use words to express numbers zero through nine.
there were 15 psychologists at the clinic
the study had 40 participants
students were in the third, sixth, eighth, 10th, and 12th grades
However, there are exceptions to this general guideline for number usage. There are cases in which you should always use numerals to express numbers, even numbers zero through nine, and likewise, there are cases in which you should always use words to express numbers, even numbers 10 and above.
Numbers expressed in numerals are covered in Section 6.32 of the APA Publication Manual, Seventh Edition
Cases in which to always use numerals for numbers
Always use numerals to express numbers in the following cases, even numbers zero through nine:
Case |
Example |
---|---|
Numbers that immediately precede a unit of measurement |
5-mg dose 3 cm |
Statistical or mathematical functions |
multiplied by 2 |
Fractions or decimals (except common fractions) |
1.5 2.27 |
Percentages |
50% 75%–80% |
Ratios | 4:1 ratio |
Percentiles and quartiles |
the 5th percentile, the 95th percentile the 3rd quartile |
Times and dates (including approximations of time) |
30 s 10 min 3 hr 2 days approximately 4 months 2 years about 6 years ago 3 decades 12:30 a.m. 6 p.m. (or 6:00 p.m.) |
Ages |
5 years old, 18 years old 5-year-olds, 18-year-olds 5-year-old children, 18-year-old adults |
Scores and points on a scale |
scored 6 on a 7-point scale |
Exact sums of money |
$10 $50 in U.S. dollars |
Numerals as numerals |
the numeral 2 on the keyboard |
Numbers in a series
Also use numerals to write numbers that denote a specific place in a numbered series when the number comes after the noun (e.g., Step 1). The noun before the number is also capitalized. This guideline applies to parts of books and tables as well (e.g., Chapter 1).
However, when the number comes before the noun, the usual guidelines for number use apply, as in the following examples.
Number after a noun |
Number before a noun |
---|---|
Year 5 |
the 5th year |
Grade 5, Grade 11 |
the fifth grade, the 11th grade |
Step 1 |
the first step |
Level 4 |
the fourth level |
Items 3 and 5 | the third and fifth items |
Question 2, Question 25 |
the second question, the 25th question |
Table 2, Figure 5 |
the second table, the fifth figure |
Column 8, Row 7 |
the eighth column, the seventh row |
Chapter 6, Chapter 14 |
the sixth chapter, the 14th chapter |
Exceptions: Do not capitalize the abbreviations for page(s) or paragraph(s), even when they are followed by a numeral (e.g., p. 3, pp. 2–5, para. 9, paras. 1–4).