Style books differ widely in their advice on written and spelled out numbers. When in doubt, check the style book which applies in your discipline. That is particularly important in Science, Mathematics, Engineering, and Business. Style manuals vary here (see Style Guides). For any given discipline and writing purpose, pick one and stick with it. For example, an author might use the CSE Manual for scholarly articles, but switch to the New York Times Manual of Style and Usage when writing an article for that publication. Students should ask for, and follow, their disciplines’ and professors’ preferences. Never mix style manual formatting within a single text unless preparing a comparison such as this one.
Purdue OWL notes that “most people spell out numbers that can be expressed in one or two words and use figures for other numbers.” If you want a cut off rule by number, spell out numbers from one to nine except in graphs, tables, and such; use figures for 10 and above as well as in tables, graphs, etc. There are exceptions:
1.When a number begins a sentence,
always spell it out.
Seventeen people called to report the incident.
Nine fairies were needed to consume the whole apple.
2.Spell out numbers below ten. Otherwise, use numerals.
Everyone over twenty-one years of age was served a complementary white wine spritzer.
For those who loathed the thought of a spritzer, the single malt scotch on the rocks cost $7.95.
“She was born in CE 1994,” he explained to his host. “CE?” she growled. You felt the need to specify the common era? So, I should let you live why?” “For my cute little chin and my winning ways,” he prompted, batting his eyelashes hopefully. She smacked his circa 1990 left arm.
The 11 participants could not be grouped in pairs, trios, or quads.
3. Addresses are numerical unless mixed. When mixed, break them up by alternating numerals and spelling.
437 Fifth Street (This keeps the reader from running the two together into a a house number (e.g., 4375 Street).
Lowercase generic street, avenue, boulevard or road and the compass point when using the plural form while capitalizing names (e.g., the house was on 10th Street: The shopping center is between 35th and 37th avenues southwest (generic) on Southwest 10th Street (specific street name). But don’t lowercase those words when the form is not plural: You can catch a bus on Second or Third Avenue. Also, lowercase and spell out avenue, boulevard, road or street when used alone: He drove down the tree-lined boulevard.
4. For dates, use figures and cardinal (1, 2, 3)–not ordinal (1st, 2nd, 3rd) numbers.
The December 18 meeting has been rescheduled.
The December 18th meeting…
On April 1, 2014, we had a pop quiz.
Or: On 1 April 2014, we had a pop quiz.
On April 1st, 2014….
5. When numbers apply to the same thing, render them the same way.
These three conference rooms hold groups of up to 8, 16, and 24 people. [This is not spelled out as eight, sixteen, and twenty-four.]
Sometimes a number needs to stand out, even when it is less than 10. For example, in résumés1 our years of experience should catch the reader’s eye:. . . including 7 years as a program manager. That’s the reason the numbers in the second rule above are in figures (numbers from 1 to 9)–so they stand out.
Recommended forms for the United States: 206-937-XXXX, 800-XXX-XXXX, 937-XXXX, NU2-XXXX,
Using periods (or dots) instead of hyphens is trendy but potentially confusing. At least for now, it is probably wise to avoid them.
Parenthesis are somewhat dated but still used by some style manuals. The Chicago Manual of Style 16th ed., for example, prefers hyphens but allows for placement of the area code in parenthesis as an alternative: (1-800) 123-1234. The 15th edition had a separate entry under “Parenthesis” (6.101); that category was completely eliminated in the 16th.
7. Temperatures: Use numerals for all except zero:
It’s 31 degrees Fahrenheit.
However, the placement of the numbers and degree symbol varies. (Ah, the things people fight about!) As a result, this is a place where it is important to check your style book.
The International Bureau of Weights and Measures (BIPM, an acronym which is French for Bureau international des poids et mesures) and the U.S. Government Printing Office both suggest printing temperatures with a space between the number and the degree symbol, as in 10 °C.
Both APA and The ACS Style Guide follow that recommendation (APA 46, ACS 224). MLA does not address the issue.
The University of Chicago Press and the Oxford University Press both employ no space between the number, the symbol, and the Latin letters “C” or “F” representing Celsius or Fahrenheit, respectively (e.g., 82°F).
Capitalize degrees Fahrenheit and Celsius (17 °C).
In general, use a word–not
a minus sign–to show temperatures below zero: It’s 8 degrees below
Temperatures get higher or lower, not hotter, warmer, cooler or colder.
8. Use numerals with a.m. and p.m.: 12:15 a.m., 7:20 p.m. When spelling it out, The Chicago Manual of Style suggests that not to use the colon, as in ten twenty in the morning or (when round numbers) eleven o’clock at night.
Time zones are usually placed in parenthesis: 2:45 p.m. (EST).
Use a period after the letters for a.m. and p.m. in the U.S.
Do you understand the abbreviations a.m. and p.m.? Before the use of standard time, (Greenwich Mean Time, time zones, etc.) most communities lacked clocks and instead used solar time. As a result, every town had its own time depending upon its latitude/longitude placement.
Noon was when the sun reached its highest point in the sky on any given day, and that changed by season: the days get longer in summer and shorter in winter.
Solar noon happens at the moment of the sun’s transit of the meridian or high point in the sky and on the sun dial. The term represents the geographical north-south imaginary line directly overhead that the sun and other celestial bodies cross. Before the sun crosses the meridian it is morning. After the sun crosses the meridian it is afternoon (post meridian or p.m.). In modern times, we still use the a.m. and p.m. designations, even though they are not technically correct.
The Latin words ante meridian and post meridian were not proper nouns, which is why we don’t use capital letters.
There is a small fuss going on between people who spell it meridian and those who spell it meridiem (with a final -m). Let’s just say right way that everybody gets to be right. Both are derived from the Latin meridies for noon. The meridiem people often also use capital letters: 1:00 A.M. Sigh. A general rule:
- In the U.S., stick with the lowercase
and use periods for a.m., p.m. except for noon or midnight.
- Expect the Brits to eliminate
the periods. Don’t get snippy: they don’t mean a form of the verb ‘to
be’ when they say 7:15 am, and you bloody well know it.
Now, walk away quietly and avoid stirring up the crazies.
9. More time trivia. You insist on more? Fine.
Times on the hour do not take zeros. Use a colon
to separate hours from minutes: 2:15 p.m., 7 a.m., not 7:00
a.m. Here’s the style for giving ranges of time: The hours
are 9:30-11 a.m. and 6-8 p.m. (or 9:30 to 11 a.m. and 6 to
8 p.m.). Yes, I know… Review my remark about not stirring up the crazies.
Avoid redundancies such as 12 noon or 12 midnight. Similarly, eliminate 8:30 a.m. this morning, or 10:30 p.m. Monday night. Instead, use noon, midnight, 8:30 a.m. today, 10:30 p.m. Monday. The construction 2 o’clock in the afternoon is acceptable but wordy.
Time zones: Capitalize the full name
of the time in a particular zone: Pacific Standard Time, Eastern Standard Time. Capitalize the region but lowercase time zone and time in shorter uses: Pacific time zone, Pacific time. Use time zone abbreviations without periods only when giving a time: noon (EST), 7:15 a.m. (PST). Don’t put the abbreviations between commas or parentheses.
10.Total number: Redundant. Drop either number or total.
- When you add 29 and 37, the total is 66.
- The number of horses in the race varies between six and nine.
AMA Manual of Style: A Guide for Authors and Editors, 10th ed., Oxford University Press, 2007. See also: AMA Manual of Style.
The Associated Press Style book. and Briefing on Media Law, Basic Books, 2013. See also: AP Style book.
Brechner, Robert Contemporary Mathematics for Business and Consumers. (Thomson South-Western, 2005).
The Chicago Manual of Style, 16th ed., University of Chicago Press, 2010. See also: Chicago-Style Citation Quick Guide.
Dewdney, A.K. 200% of Nothing: An Eye-Opening Tour Through the Twists & Turns of Math Abuse & Innumeracy. (John Wiley and Sons, 1993)
Hazlett, Curt. “Tips to make numbers your best friend.” Web.
The MLA Handbook for Writers of Research Papers, 7th ed., Modern Language Association of America, 2009.
MLA Style Manual and Guide to Scholarly Publishing, 3rd ed., Modern Language Association of America, 2008.
The New York Times Manual of Style and Usage, Times Books, 1999.
Norquist, Richard. “Choosing a Style Manual and Style Guide: Popular Style Guides for Students, Researchers, and Professionals.” About Education. About.com. n.d. Web. 28 June 2014.
“Numbers.” University of Minnesota. n.d. Web.
The Owl. “Numbers” Purdue University’s Online Writing Center. 2006 Web.
Publication Manual of the American Psychological Association (commonly known as the APA Style Manual), 6th ed., American Psychological Association (APA), 2009. See also: APA Style. Web. 28 June 2014.