Section 3. Numbers

3.1 General Rules

For detailed guidelines on the correct style for numerical expressions, consult Chapter 5 of The Canadian Style. At CMH and CWM, the following general rules apply:

• Spell out numbers from one to nine and use digits for numbers 10 and above.
• Spell out round numbers when they appear infrequently: twenty, thirty, one hundred, etc.
• Spell out any number that appears at the beginning of a sentence, as in “Twenty-four hours had passed before he knew it.”
• For large round numbers (1 million and over), use a digit and spell out million, billion, trillion, etc. (for example, 1 million, 3 billion, 5 trillion).
• Spell out and hyphenate fractions (for example, two-thirds).
• Use digits in statistical or comparative texts, as in “3 apples and 12 oranges.“
• Always use digits for percentages. Spell out the word “percent” in texts and use the percentage symbol (%) in tables, charts and financial texts.
• For page ranges, do not repeat hundreds: 256–63, not 256–263.
• Use a comma to indicate thousands: 1,000, not 1000 or 1 000. The exception to this rule is its application to years (see section 3.3).
• The style for ordinals is the same as the style for numbers. Ordinal suffixes should not be superscript: 150th not 150^th.

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3.2 Measurement and Age

Always use digits before a unit of measurement, and only abbreviate the unit of measurement when space is limited or in tables and charts. Always include a space between the digit and the unit of measurement (for example, 12 metres or 12 m).

Always use metric measurements. In historical texts and in quotations, where it may be difficult to avoid the Imperial system, give the equivalent metric measurement in parentheses, like this: “5 pounds (2.3 kilograms).” An exception to this rule is when referring to floor space, where square footage is still the predominant unit of measurement in Canada. In this case, the measurement may be given in Imperial units with no metric equivalent (for example: “The upcoming Canadian History Hall will cover an area of 40,000 square feet.”).

When abbreviating Imperial units, end with a period (for example, 2 ft.). If there is more than one element, no punctuation is used: “2 feet 12 inches,” not “2 feet, 12 inches.” Abbreviated metric units do not take a period: m for metre, kg for kilogram, etc. Litre is abbreviated with a capital L, and millilitre is abbreviated as mL.

Always use digits when expressing ages, as in “He is 82 years old.” When expressing a range of ages, use this style: “ages 6 and up” or “from ages 6 to 12.” Also, be consistent: 16 years old and 12 years old; or 16 years of age and 12 years of age. (See also “2.2 Compound Words and Hyphenation.”)

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3.3 Dates

Full dates are to be expressed as “month day, year,” as in “May 17, 1986.” If a numerical abbreviated form must be used, such as in labels, charts, tables or chronologies, the order to be used is day/month/year, as in “17/05/86” or “17-05-86” for May 17, 1986 (either style is correct, as long as it is consistently applied). When expressed in a sentence, do not use a comma after the year in dates, as in “October 12, 1987 was the sunniest day of the year.”

For periods of time:

• Connect written dates with the word “to” and include the year only once when time span is within one year: for example, January 4 to May 17, 1984; but August 30, 1983 to January 4, 1984.
• Repeat the century in range of years, even if the range is within one decade: 1967–1969 (note use of en-dash in this case).
• Use “1970s” to refer to the decade (note that there is no apostrophe).

It is CMH style to use the Christian calendar abbreviations BC and AD, if necessary, to designate years. For years of four digits or less, no comma is used, as in “AD 1960.” For years of five digits or more, use a comma, as in “15,000 BC.” The abbreviations BC and AD should be used only if they are absolutely necessary.

Use digits when referring to a century (for example, 18th century). Note that expressions of century are never hyphenated.

Spell out the word “circa” in a sentence; abbreviate as “c.” in labels or when space is limited. In popular texts, it is best to avoid “circa,” replacing it with “around” or “about.”

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3.4 Money

Always use digits when expressing amounts of money.

Never use the symbols K, M or B for thousand, million or billion.

When the text refers only to Canadian dollars, use $ alone: $20.40. If more than one currency is referred to, use CA$ for Canadian dollars (CA$20.40) and US$ (no periods) for U.S. currency (US$19.80). Where some amounts include portions of a dollar, all amounts must follow the same style (for example, Tickets: $20.00; Children 2–12: $10.50).

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3.5 Time

In all English texts, use a.m. and p.m. (not the 24-hour clock) in expressions of time. When the time is on the hour, the “:00” should be omitted, as in “8 a.m.” and “4 p.m.” (for example, “Tours depart at 2, 3:15 and 5 p.m.” and “Demonstrations will take place at 10 and 11:30 a.m., and at 2 and 3:30 p.m.”). Note in these examples that “a.m.” and “p.m.” are not repeated in consecutive expressions of time.

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3.6 Phone Numbers

Do not use parentheses around the area code. Instead, use a non-breaking hyphen after the area code and between groups of digits within a telephone number, like this: 819-555-5555. This style applies to all telephone numbers in Canada and the U.S., including cell phone, pager, facsimile and teletype (TTY) numbers; toll-free and long-distance numbers (for example, 1-800-555-5555); and alphanumeric numbers, such as 1-800-TERMIUM and 1-877-RESERVE.

For international use, Canadian telephone numbers should be expressed as follows: +1-819-555-5555. The + sign reminds people calling from abroad to dial the international prefix for the country they are calling from, before dialling “1,” which is the country code for Canada.

Do not use hyphens between the digits in service codes such as 411, 611 and 911 (for example, “In case of emergency, dial 911.”).

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