5.02 Round numbers

Write out numbers used figuratively:

  • a thousand and one excuses
  • They may attack me with an army of six hundred syllogisms.
  • And torture one poor word ten thousand ways.

Numbers in the millions or higher should be written as a combination of words and figures:

  • 23 million
  • 3.1 million
  • There were more than 2.5 million Canadians between the ages of 30 and 40 in 1971.

When such compound numbers are used adjectivally, insert hyphens between the components (see 5.05 Adjectival expressions and juxtaposed numbers):

  • a 1.7-million increase in population

Whether or not it is used adjectivally, the entire number (numeral and word) should appear on the same line.

Numbers with a long succession of zeros should normally be rewritten. Thus 2.6 million is preferable to 2 600 000.

Numbers are normally rounded to no more than three significant digits. Thus 2 653 000 becomes 2.65 million, not 2.653 million.

The proper form for large numbers that must be written in full is as illustrated:

  • one hundred and fifty-two thousand three hundred and five

The practice of writing a number in full and then repeating it in numerals in parentheses should be reserved for legal documents:

  • nineteen hundred and ninety-six (1996)