1. Spell out single-digit numbers from zero to nine, but use words instead of figures at the start of a sentence.
2. Use numerals with abbreviated units of measurement.
3. Prefer cardinal to ordinal numbers in dates.
4. Use numerals for years, except at the start of a sentence.
5. Decades and centuries may be written in words or numerals.
6. To emphasize the exact time or with a.m. and p.m., use numerals. When the exact time is not important, or with o’clock, you may use either words or numerals.
7. Hyphenate simple fractions (a two-thirds majority), but use figures for decimals (4.023) and mixed fractions (7¼ feet long).
8. For amounts of money, follow the general rule. Note that some style manuals (e.g., the AP Stylebook) recommend always using numerals.
The general rule is to spell out numbers from zero to nine, and use numerals for numbers from 10 onward. Exceptions exist—for example, words instead of figures are used at the start of a sentence. The different style manuals also have their own specific guidelines about spelling out numbers versus writing them as figures (or numerals).
1. Spell out single-digit numbers (from zero to nine), and use numerals for others.
2. Spell out numbers that begin a sentence .
3. To aid with readability, hyphenate two-digit numbers when spelling them out.
4. Follow the rules listed above for whole numbers used in combination with million, billion, trillion, and so on.
5. To improve clarity, skip the and in numbers such as 7,543 when spelling them out.
6. Maintain consistency in using numerals or words within a sentence. If any of the numbers within one category is greater than nine, use numerals for all numbers within that category.
However, if the only reason you use words instead of numerals is because the number is at the start of a sentence, you can use numerals for the following numbers even if they are of the same category.
Don’t be afraid to reword to improve readability.
The Chicago Manual of Style specifies some exceptions to the general rules above.
1. Spell out whole numbers from zero to one hundred (instead of only those from zero to nine).
2. Also spell out whole numbers followed by hundred, thousand, or hundred thousand.
Use numerals as usual for other numbers greater than one hundred.
Remember to spell out numbers that begin a sentence.
If this feels clunky, reword.
The AP Stylebook suggests using numerals with million, billion, etc. (except at the start of a sentence).
Add st, nd, rd, and th as appropriate to create ordinal numbers (which indicate the position of something in a sequence). The general rules about using words or numerals apply to ordinal numbers as well (including the exceptions in Chicago style).
Most style manuals recommend displaying the letters in ordinal numbers as regular text rather than superscripts (to ensure uniform presentation across fonts.)
With units of measurement (including SI units), use numerals, especially when writing in a technical context. In particular, always use numerals with abbreviated units.
In nontechnical writing, treat quantities such as distances, time periods, and lengths based on the general rule.
In dates, skip the ordinal number (May 5 instead of May 5th or May 5 th ), and use a numeral for the day.
When writing as it would be read aloud (for example, in creative writing), follow the general rules.
British style generally follows the day-month-year date format, while Americans use month-day-year. Dates written in sentences also read differently.
Write years in numerals, but spell out the year if it starts a sentence.
Decades can be written in words or numerals.
In names of decades and centuries, an apostrophe may or may not be placed before the s.
Note that in most styles (including Chicago, APA, and AP), the apostrophe is omitted.
Names of centuries can either be spelled out or referred to using numerals. Do not capitalize.
Rules for how to write centuries vary across style manuals. The Chicago Manual of Style and the MLA Handbook recommend spelling out the names of centuries.
The AP Stylebook follows the general rule: spell out single-digit century names and use numerals for double digits. Stay consistent in usage within a text.
Use numerals to emphasize exact times on the clock face.
With o’clock, you may use either words or numerals.
You can also spell out quarter and half hours in text and use words for the numbers.
Noon and midnight are usually referred to as such instead of as 12 noon and 12 midnight.
Stay consistent in referring to hours and minutes within a category.
When speaking of time using the 24-hour system, use numerals. A colon appears between the hours and minutes only if the word “hours” is not used.
With a.m., p.m., and the 24-hour system, time markers like in the morning or at night are redundant.
Express decimal fractions in numerals.
When the fraction is less than one, a zero is normally inserted before the decimal point.
All quantities other than 1 are considered plural, even those less than 1.
Spell out simple fractions . Such fractions are usually hyphenated to improve readability.
For mixed or improper fractions, use numerals.
To express a percentage , use numerals, except at the start of a sentence.
If the percentage contains digits after the decimal point, avoid using it at the start of a sentence.
Percent is more common in American English and per cent in British. The symbol (%) is used more often in technical copy than in business or other writing, and is preferred in tables, charts, and graphs.
No space is left between the numeral and the symbol %, except in scientific and technical publications that follow SI style.
Spell out amounts of less than 10, and use numerals for the rest. Also remember to use words instead of numerals if the amount appears at the start of a sentence.
The AP Stylebook suggests always using numerals with million, billion, etc., and with units of money.
Numbers that follow nouns to refer to things in a series are always written as numerals.
the second chapter of a series of chaptersWhether to use numerals or words is a matter of style rather than grammar . What’s important is to stay consistent within a document. A style manual can help you do this. Mixing styles (e.g., writing percent in one sentence and % in the next) can make your thesis, report, or presentation look messy and unprofessional. If you don’t have a style guide, consider creating your own style sheet from the guidelines outlined above. Finally, remember that consistency and common sense are more important than any rules and exceptions. In short, break a style rule if you must, to improve readability.
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