Site Title

Numbers

In General

The following guidelines apply to the majority of CU-Boulder writing except for scientific, statistical, technical, and mathematical writing.

Spell out one to nine. Use numerals for 10 and above.

• Since 1999, CU-Boulder students have won three Marshall, two Truman, and four Udall scholarships. They have also won 11 Goldwater awards.

Exceptions: Use numerals for percentages, decimals, credit hours, GPAs, book sections and pages, quantities combining whole numbers and fractions, and when symbols rather than abbreviations are used for units of measure.

Use the word percent in formal running text. Use the percent sign in tables, charts, scientific and statistical copy, and some informal and promotional copy. Whichever you choose, be consistent throughout a document.

• We printed the first draft on 8.5" 3 11" paper.
• In his first semester, when he carried 16 credit hours, he earned a 3.10 GPA while spending
• 30 percent of his time on a work-study job.
• You’ll find the answer in Chapter 2 on page 31.
• She gave five dollars to the CU Foundation, which was 8 percent of her annual dividend check.
• Her brother gave $5.50 to the CU Foundation.
• Her sister gave $5 million to the CU Foundation.
• In the following table, 3 mi. and 75 ft. are approximations.

• Spelling out large round numbers is preferred.
  • She gave the museum more than two hundred thousand artifacts.
• Use a combination of numerals and words with numbers in the millions and larger.
  • The population increased by 2.3 million.
• Use a comma for numbers with more than three digits unless they represent SAT scores or years.
  • Resident tuition for 2007–08 was $3,317 per semester.
  • The book, which was published in 2007, has 1,229 pages.
  • His combined SAT score was 1235.
• Spell out numbers at the beginning of a sentence or rephrase the sentence to avoid beginning with a number.
  • Forty-nine students received the new degree at the May commencement.

Adjacent Numbers

When a sentence has two numbers adjacent to each other, using a combination of numerals and spelled-out numbers can help avoid confusion and, in some cases, is actually required. If one of the numbers is a unit of measurement, leave that number a numeral. In other cases, spell out the shorter of the two numbers.

• The play’s set included twelve 8-foot-high plaster pillars.
• They distributed 334 twelve-page brochures.

Dates

The U.S. preference is for styling dates as month, day, and year. Do not use ordinal numbers in dates.

• New parking permits go on sale January 8, 2007.
• NOT New parking permits go on sale January 8th, 2007.
• NOT New parking permits go on sale 8 January 2007.

Footnote Numbers

Asterisks and superscripts follow punctuation marks (except a dash) in running text and are placed outside a closing parenthesis.

• Be sure to enter your social security number,¹ your phone numbers (daytime and evening)² with area code, and your mother’s maiden name.³

Fractions

Hyphenate fractions when they are spelled out:

• Two-thirds of the class was late.
• A four-fifths majority voted in favor of the amendment.

Inclusive Numbers

When dealing with ranges of numbers (such as page numbers and years), carry over all the digits that change and include at least two digits for the second number. Use an en dash rather than a hyphen between the numbers.

• pages 1,004–05
• 1991–94
• 1889–1922

Unless the century changes, inclusive years should be styled with only the last two digits of the second number (1899–1900, but 2001–02). Inclusive years on publication covers, however, can be styled with all four digits of the second number (2001–2002 versus 2001–02) at the designer’s discretion.

Note that in running text, the en dash is not an acceptable substitute for the word to unless the numbers are in parentheses.

• She taught anthropology from 1952 to 1992.
• She taught anthropology at CU (1952–1960), Harvard (1960–1988), and Berkeley (1988–1992).

Metric Measures

If you are writing for an international audience (for example, writing a brochure to recruit international students for a new program or publicizing an international conference), include metric measurements.

• The CU-Boulder Main Campus averages 5,400 feet (1,645 meters) in altitude. The average Boulder daytime high temperature in July is 87°F (31°C).

Money

When a relation between two or more similar amounts is expressed, the dollar symbol may or may not be repeated, but use an en dash to denote range. If fractional amounts over one dollar are used in any reference, be consistent and use them throughout, even if it’s a zero amount.

• Sweatshirts are available from $20.99 to $75.00.
• She estimated that an endowed chair would cost $1–2 million.

Multiple Numbers in a Sentence

If a sentence includes multiple numbers that apply to the same general category, and if one of the numbers must use a numeral, use numerals for all the quantities of that category.

• The multiline 44-button telephone is designed to handle more than one call at a time and is equipped with 10 call appearance/feature function buttons, 24 feature function buttons, and 7 display control buttons.

Ordinal Numbers

Spell out ordinal numbers from first to ninth.

• She placed fourth out of 525 competitors.
• The 21st century was fodder for many imaginative novelists and entrepreneurial visionaries during the latter half of the 20th century.

Room Numbers

Campus room numbers should be referred to with the name of the building and the room number, in that order. Do not use the word room or hall.

• The Buff OneCard Office is located in Willard 182.

Telephone Numbers

Now that all local numbers require the use of an area code, do not put the area code in parentheses.
Instead, simply use a second hyphen: 303-735-1079.

Time

Use numerals with a.m. or p.m. (small caps or lowercase letters) to indicate specific times. Use noon and midnight in place of 12:00 p.m. and 12:00 a.m., respectively, for clarity.

• The lecture will begin at 2:30 p.m.
• I’ll extend office hours this week until about five o’clock.

Years and Decades

There are multiple formats for referring to decades. In running text, spelling out the decade (first example) or using the full numeric decade (second example) is preferable. Use the abbreviated numeric decade format in very informal copy or in lists where space is limited. Do not use an abbreviated format if there could be any confusion about the century. Do not use an ’s in numeric decades (1880s or ’80s, not 1880’s or ’80’s).

• the eighties
• the 1880s
• the ’80s

Use the correct placement for a.d. and b.c. (small caps).

• Hannibal died in 183 b.c.
• King George IV died in a.d. 1830.