Basics

Zero to Nine - Spell out all single-digit numbers from zero to nine (e.g., ‘two’ instead of ‘2’).

10 or Above - When a number(s) is 10 or above in a paper, then the numeral(s) are typically expressed as a numeral (e.g., 10).

Zero to 100 - Spell out whole numbers (e.g., 'one or twenty' instead of '1 or 20') from zero to one hundred.

Beginning a Sentence - The word format of a number (e.g., 'Ten' instead of '10') should be used with any numbers that begin a sentence or title/heading.

Expressions

Mathematical Expression - When a number is cited in statistical/mathematical format as a percentage or a fraction, it should be expressed as a numeral (e.g., 16%).

Measurement Expression - When a number is stated directly before a unit of measurement it should be expressed as a numeral (e.g., 10mg).

Time, Date, & Age

Time, Date, and Age - When a number is expressed as a time, date, or age then it is typically written as a numeral (e.g., 20 years).

Punctuation & Roman Numerals

Plural (No Apostrophe) - Whenever numbers are written in plural form they should not contain an apostrophe (e.g., 50s, sixties).

Comma Use - Commas are typically inserted for every three digits in a number unless commas do not commonly break up the number, such as in the instance of page numbers, temperature, serial numbers, etc.

Roman Numerals - If it is the norm to use Roman Numerals within a specific frame (e.g., Super Bowl), then it is best to not change to Arabic Numerals. If, however, it is an instance of seriation used throughout the paper, then Arabic Numerals are more commonly used.

Decimals - Decimals should have a zero before the decimal point if the number is less than one.

Common, Ordinal & Cardinal

Common and Accepted Numbers - When expressing common fractions and commonly recognized numbers, write out the number as a word (e.g., one sixth, or Ten Commandments).

Ordinal and Cardinal - Ordinal numbers should be treated the same as cardinal numbers (e.g., ordinal - sixth grade, cardinal- six grades).