Style Rules for Numbers



1.  Spell out numbers lower than 10 in non-scientific text.

2.  Treat numbers in the same sentence alike: if there's a two-figure number in the sentence, make all the numbers figures, as long as the figures all relate to the same items.


  • The students collected 14 books for the sale, 3 of which were first editions.
  • Having four meetings made it possible for the 15 committee members to collect 160 used books.

3.  Use either a figure or a word, not both. Five rooms, not five (5) rooms. Delete the parentheses and the 5.

4.  Use the up-to-10-spelled-out/higher-than-10-numeral rule for ordinal numbers (first, second, 12th, 23rd, etc.). This applies to numbered street names as well: Fifth Avenue, 23rd Street.


  • In street addresses, building numbers are usually written in arabic numerals: 5801 Ellis Avenue.
  • When a building's name is also its address, the number is spelled out: One Park Place.

Credits, Units

  • Always use numerals: 3 credits; 18 credits in history; a 3-credit course; 4 units of English; 1 unit of geometry; 2 units of a foreign language. Also, use numerals when referring to credit hours. (Note use of "in" with credits and "of" with units.)


  • No apostrophe: 1920s; 1980s; mid-1970s.
  • Spell out thirties; forties; fifties; sixties; etc.


  • Fractions generally are too cumbersome to spell out and should be expressed in numerals, but judge each case on its own.


The obstacle was a 3 1/2-foot fence.

They had finished about one-third of the course.

Graduation Years

  • Use an apostrophe (or right-side single quote) preceding the two-digit class year; no comma after the name; no comma before degree designation.


Attending the Homecoming reunion were Elise Adams '64 and John Andrews ' 88, '90.

Harold Jones '74 BSEE was the first NCE graduate to win the award.

More Than/Over

  • When referring to something that can be counted, use more than rather than over.


More than fifty people attended (not Over fifty people attended).

But: Jason is over six feet tall.

Multiple-Digit Numbers

  • Use a comma for four-digit and larger numbers (except dates): 3,500; 60,000.
  • For very large numbers, use figure and word: 1.2 million, $90 million.

Numbers at the Beginning of a Sentence

  • Always spell out numbers at the beginning of a sentence.
  • Rearrange the sentence if spelling out the number makes it cumbersome.
  • Avoid putting numbers next to numbers -- separate the numbers with words if possible.

Parts of Books

  • Use numerals when you are referring to parts of a book.


Chapter 4; Table 2.5; page 4


  • Always use numerals.
  • Spell out percent in text: 5 percent; 9.2 percent.
  • Use the % symbol in charts, graphs, and scientific and mathematical material.

Quantities as Numerals with Abbreviations

  • If a quantity is used with an abbreviation, the quantity always should be expressed in numerals.
  • If a symbol is used with the quantity, use a numeral.
  • For two or more in quantity, the symbol should be repeated.


3" x 5"; 30' x 50'; 80 km; 2 tsp.

Round Numbers

  • Approximate figures in hundreds, thousands, or millions should be spelled out.
  • Very large figures should be written as numerals, whether they are approximated or not.


The company distributed more than one million books.

The nation's population neared 2.3 billion.

Times of Day

  • Use the figure and a.m. or p.m. in both text and schedule listings.
  • Because time designations are not always on the hour, for consistency, use :00 with times that are on the hour.
  • Note that a.m. and p.m. are not capitalized.
  • When possible, drop p.m. or a.m. rather than repeat it.
  • To avoid confusion, use noon and midnight rather than 12:00 p.m. (noon) and 12:00 a.m. (midnight).


Classes scheduled for 5:00 p.m. and later have been canceled for today.

The meeting will be held from 4:30 to 6:00 p.m.

I thought he said to meet him at midnight, but he meant that I should meet him at noon.