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Chicago Citation Style Guide

Using Numbers in an Essay

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


  •   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.

When Should I Use Numerals?

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


  • 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.