MLA Style Guide

Spell out numbers that can be expressed in either one or two words.  

Examples:

•   one million
•   ninety-nine
•   one hundred
•   fifteen hundred

Always spell out the number if a sentence begins with a number.

Example: Two thousand twelve was an election year in the United States.

Use numerals if you are writing an essay about a scientific subject or an essay that includes frequent use of numbers, like statistical findings. 

Always use numerals:

•  in front of units of measurements. Example: 5 millimeters
•  with abbreviations such as 6 lbs., 4:20 p.m., $9, 2”, 4%.
•  in dates: Example: April 1, 2014
•  in decimal fractions: Example: 9.2

Exceptions: 

• For large numbers, you may use a combination of numerals and words. Example: 4.5 million
• In general use numerals with % signs, however, you may spell out percentages or amounts of money if you can do so in three words or less. Example: five dollars, forty-five percent, sixty-eight cents.