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Expressing Numbers

Spell out the whole numbers one through nine. Write other numbers using digits. (In humanistic works, you may choose to spell out all whole numbers less than 100.) Treat ordinals in the same way as cardinal numbers.
  • I met seven people.
  • John met 14 people.
  • I was the eighth person.
  • John was the 15th person.

Always spell out numbers at the start of a sentence. Reword sentences to avoid spelling out large numbers.

  • Incorrect: 16 cars were parked on the street.
  • Correct: Sixteen cars were parked on the street.
  • Incorrect: 2134 children attended the school last year.
  • Incorrect: Two thousand one hundred thirty four children attended that school last year.
  • Correct: Last year, 2134 children attended that school.

Spell out round numbers and approximations.

  • The tree is about sixteen feet tall.
  • I have told you a thousand times not to do that.
  • The car is worth less than six thousand dollars.

Round numbers and approximations greater than one million may be expressed with a combination of words and digits. Exact figures should be expressed using digits.

  • The city was home to 3 million inhabitants.
  • The city was home to 3 256 092 inhabitants.

Use digits for numbers used as nouns, exact measurements, decimal fractions, and percentages.

  • Multiply the result by 5.
  • The screws are 4 inches long.
  • The best price for 4.5 m is $23.50.
  • The sales tax was raised to 9%.

The International System of units (SI units), commonly known as the metric system, requires that digits be used with abbreviated units, and spelled-out numbers are used with spelled-out units.

  • Incorrect: The road was 2 kilometres long.
  • Correct: The road was 2 km long.
  • Correct: The road was approximately two kilometres long.

Related numbers should be expressed consistently.

  • Incorrect: He worked 40 hours the first week, and only seven the second week.
  • Correct: He worked forty hours the first week, and only seven the second week.
  • Correct: He worked 40 hours the first week, and only 7 the second week.

When two numbers are adjacent, spell out one of them. Usually, the one with fewer letters is spelled out.

  • The couple had their choice of two 3-bedroom apartments.
  • Another couple had to decide between 3 two-bedroom apartments.