Basics

Zero to Nine - Typically 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 - It is acceptable to 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 (MLA, Chapter 3, 3.5.2, 82).

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%) (MLA, Chapter 3, 3.5.4, 83).

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

Plural (No Apostrophe) - Whenever numbers are written in plural form they should not contain an apostrophe (e.g., 50s, sixties).(MLA, Chapter 3, 3.2.7g, 75).

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. (MLA, Chapter 3, 3.5.3, 83).

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).