Rules on the Use of Numbers in Sentences

As in the case with capitalization and abbreviations, the rules for handling numbers in text are complex and varied. In this book, we provide guidelines that are generally agreed upon by many experts.

Arabic Numbers and Roman Numerals

Most of the figures used today are expressed in Arabic numbers. However, Roman numerals are still used in names, documents, books, dates, and so on. Following is a list of Arabic numbers and their equivalents in Roman numerals.

Table of Roman and Arabic Numbers

Figures or Words

Whether numbers should be spelled out or written in figures depends on several factors. Among them are the size of the number, what it stands for, and what kind of text it appears in—business, personal, scientific, or scholarly.

In general, use the “rule of ten” in determining whether to spell out a number or express it in figures. Under the rule of ten, spell out numbers ten and under (two, five, seven) and any number that is divisible by ten (twenty, sixty, eighty). All other numbers over ten are written in figures.

    • Governors from six states urged passage of the water-rights bill.
    • I ordered three dozen boxes of mint candies.
    • Did you know this book has 1,345 pages?
    • She turned 39 last year but doesn’t look over 25.
    • Our flight will arrive in Hong Kong in 12 hours.
    • We now have a thirty-year mortgage to pay off.

Round Numbers. Numbers used as approximations in place of specific figures are often spelled out, even when expressed as hundreds of thousands.

    • The march drew an estimated thirty-one thousand people.
    • About three to four hundred thousand people were left homeless by the floods.
    • Some form of sun worship has existed in human culture for nearly twelve thousand years.

Very large numbers are usually expressed in figures followed by million, billion, trillion, and so on.

    • It would cost $3.5 billion to send a piloted probe to Jupiter.
    • The gross national product is nearly $257 trillion.
    • The greater metropolitan Chicago area contains more than 7.2 million people.

Ordinal Numbers. The same rule of ten holds for ordinal numbers (first, second, third) as well.

    • Luciano ranked fifth in a class of 356 students.
    • My two horses came in first and ninth in the afternoon race.
    • The 25th article in the bylaws hasn’t been revised.
    • Bjorn was given the 232d and 233d numbers out of 655.

Notice that the form for second and third is d and not nd or rd.

Consistency. The exception to the rule of ten occurs when numbers under and over ten are used in a series or to refer to the same item in a sentence or paragraph. For the sake of consistency, numbers under ten are frequently expressed in figures.

    • Joan’s family has 5 children, 11 cats, 3 turtles, 15 gerbils, and 2 canaries.
    • In ten years, the population has grown from about 8,000 to 154,567. (Ten is spelled out because it is not related to the population figures but stands by itself. Compare that sentence to In the past 10 to 15 years, the population has grown from about 8,000 to 154,567. In this case, the figure 10 is used because it is related to the same category—years—as the number 15.)
    • We climbed the 102-story building all the way to the top, but four of us had trouble making the last 2 or 3 stories. (The figures 2 and 3 refer to the same item—the number of stories. Four, however, refers to a separate category, the number of people, and is therefore spelled out.)

Numbers Together. In some instances, numbers are used next to each other for more than one item in a sentence. Generally, to avoid confusion, the smaller of the two figures will be expressed in words.

    • We developed twenty-five 35 mm slides yesterday.
    • The stock cars will go 14 two-mile laps.
    • I’d like 250 thirty-seven-cent stamps.
    • He bought twelve 65-cent labels.

First Word in Sentence. Spell out numbers that begin a sentence, regardless of any inconsistency this may create in the rest of the sentence or paragraph. As a general rule, if the sentence contains more than one figure, or if the figure is large, try to rephrase the sentence so that the number does not come first.

    • Twenty-seven people attended the banquet.
    • Fifteen cars piled up on the freeway, and 37 cars blocked the exit ramp.



Twenty out of every 100 people interviewed preferred daytime baseball games.

Daytime baseball games were preferred by 20 out of every 100 people interviewed.


We found that 20 out of every 100 people interviewed preferred daytime baseball games.

Nineteen twenty-seven marked the first solo transatlantic flight in aviation history.

The year 1927 marked the first solo transatlantic flight in aviation history.


Express exact ages in figures. Approximate ages can be expressed in words or figures, but be sure to use the same style throughout.

    • Theodore Roosevelt was elected Vice President when he was only 42.
    • Andrea is 7 and Van is 14.
    • The baby is 2 years and 6 months old.
    • She was about sixty when she first traveled to Africa.
    • My father is nearly ninety.


Roman numerals are used to distinguish among members of the same family who have identical names. No comma is used between the name and Roman numerals.

    • John Ellis III
    • Bror von Blixen IV

Roman numerals are also used to differentiate sovereigns, emperors, and popes with the same name. Modern usage, however, permits Arabic numerals in some cases.

    • John XXIII or John 23d
    • Elizabeth II
    • Richard III

Vehicles such as ships, spacecraft, cars, and airplanes may also be given Roman numerals to distinguish them from previous models with the same name. Although earlier spacecraft in the NASA program carried Roman numerals, current practice is to use Arabic numbers.

    • America IV
    • Mercury II
    • Bell X-15
    • Bluebird III
    • Apollo 12
    • Saturn 2

Governmental Designations

Unlike with the “rule of ten,” whether numbers are spelled out in govern- mental designations often depends on whether they are less than one hundred.

Governments. Ordinal numbers are used to designate particular dynasties, governments, and governing bodies in a succession. The numbers are spelled out if they are less than one hundred and precede the noun. In most cases, they are capitalized.

    • The 102d Congress
    • First Continental Congress
    • Eighty-sixth Congress
    • Third Reich
    • Twelfth Dynasty
    • Fourth Republic

Political Divisions. Numbers one hundred or less indicating political divisions should be spelled out in ordinal form and capitalized.

    • Forty-second Ward
    • Thirty-fifth Precinct
    • 123d Congressional District Circuit
    • Court of Appeals for the Sixth Court

Military Units. Spell out in ordinal form numbers one hundred or less that indicate military subdivision.

    • The 101st Airborne
    • 156th Fighter Wing
    • Second Battalion
    • Eighty-sixth Regiment
    • Seventh Fleet
    • 110th Artillery


Here are guidelines for using numbers in the names of organizations.

Unions and Lodges. Use Arabic numbers to express figures designating local branches of labor unions and of fraternal lodges.

    • Masonic Lodge No. 335
    • Flight Attendants Union Local No. 127
    • American Legion Post No. 34

Churches. Spell out ordinal numbers used with religious organizations or houses of worship.

    • First United Methodist Church
    • Seventh-day Adventists
    • Twenty-second Church of Christ, Scientist
    • Second Baptist Church

Corporations and Civic Events. Numbers used in the names of companies or civic events may be spelled out or expressed in Arabic or Roman numerals. You will need to follow the particular organization’s style.

    • Fifth Third Bank
    • 1st Federal Savings & Loan
    • 3rd Annual Sport Jamboree
    • XXIV Olympics

Addresses and Thoroughfares

House numbers should be expressed in figures, except for the number one. Numbered streets one through ten are spelled out.

    • One East Superior
    • 354 Crain Street
    • 1274 23d Street
    • 32 Second Avenue

When the address is part of a building’s name, the number is usually spelled out.

    • One Magnificent Mile
    • Thirty-three Prudential Plaza

Use figures for all state and federal highways.

    • U.S. Route 66 (U.S. 66)
    • Interstate 294 (I-294)
    • Arizona 103
    • County Line 24

Time of Day

When time is expressed in even, half, or quarter hours, the numbers are generally spelled out.

    • The movie starts at a quarter past four.
    • I didn’t get home until twelve o’clock last night.
    • The meeting is set for two o’clock this Thursday.

Figures are used when the exact time is given or in designations of time with AM or PM. Never use o’clock in either of these cases.

    • The train pulled into Lisbon at 12:33 in the morning.
    • The full report should be on the 6:30 news.
    • Precisely at 5:00, I saw him leave his apartment.
    • We’ll meet here again at 5:15 PM tomorrow.

He called at 12:20 AM to say he had locked himself out of his house. In the 24-hour time system, figures are always used. There is no punctuation between the hour and minutes.

    • Our ship docks at 0615 on Wednesday.
    • Registration hours are from 0900 to 1130 and 1300 to 1530 every day except Sunday.


This section presents guidelines for the use of numbers in dates.

Day and Month. When writing dates, you can use either day/month/year or month/day/year.

    • On 7 August 1975, we left for Egypt.
    • I sent the letter on April 14, 1983, but I never received a reply.

Notice that when the month/day/year form is used, the year is set off by commas before and after it.

When the day and month are used alone, references to another date in the same month are spelled out.

    • The order was dated 6 July. We sent your package out on the seventh.

You may use either words or figures for the day when it occurs alone or when the month is part of a prepositional phrase in a sentence; just be consistent.

    • Paychecks are issued on the 5th of each month.
    • Paychecks are issued on the fifth of each month.
    • On the 12th of April, I signed the contract.
    • On the twelfth of April, I signed the contract.

Month and Year. When dates are identified only by month and year, no internal punctuation is necessary.

    • She entered school in September 1979 when she turned 21.

The Year Alone or Abbreviated. Unless they begin a sentence, years are expressed in numbers no matter how large or small they may be. No commas are used in the figures.

    • The Egyptian Nile Valley was heavily populated by 3500 BC.
    • Early records indicate the settlement was occupied from 34 BC to AD 67.

Abbreviations of years drop the first two figures and substitute an apostrophe.

    • the class of ’69
    • the spirit of ’76
    • They were married in ’41.

Centuries and Decades. References to particular centuries and decades are spelled out in lowercase letters (as long as there is no confusion about what century is being referenced).

    • We are at the beginning of the twenty-first century.
    • Social upheaval during the sixties gave way to political conservatism in the eighties.

If decades are identified by century, be sure to use the same style throughout.



The 1880s and ’90s were a time of colonial expansion.

The 1880s and 1890s were a time of colonial expansion.

Notice that there is no apostrophe before the finals after the year.

Eras. Use figures to express dates and words to express centuries whether the era designation comes before or after the date involved. The most frequently used era designations are as follows (notice no periods are used):


before Christ (twelfth century BC)


(anno Domini) in the year of the Lord (AD 1940)


(anno Hegirae) in the year of (Muhammad’s) Hegira (AH 736)


(anno Hebraico) in the Hebrew year (AH 1426)


before the common era (2713 BCE)


before the present (5892 BP)

The designations AD and AH precede the figures, while the other designations follow them. However, both AD and AH follow centuries expressed in words.

    • 378 BC
    • 13400 BP
    • fourth century BC
    • AD 1945
    • AH 677
    • fifteenth century AD


Use figures to express sums of money whether foreign or U.S. currency. However, spell out small sums of money when the figure stands alone or serves as an adjective.

    • The car cost $2,560.
    • I changed $4 for £6.
    • I remember when movies cost twenty-five cents.
    • They charge a ten-dollar fee.

If an abbreviation rather than a symbol is used for foreign currency, leave a space between the abbreviation and the figure.

When two currencies share the same symbol (for example, the $ symbol in Canadian and U.S. money), use a prefix or suffix to distinguish between the two.

    • His hotel bill totaled $127.50 Canadian ($87.50 U.S.) for a three-day stay.

Fractional and Large Amounts. Fractional amounts over one dollar are expressed in figures. Very large amounts may be expressed in figures and units of million, billion, or trillion.

    • I bought this book for $12.00 and then saw the same item on sale for $3.50.
    • The clerk added up the charges of $66.21, $43.90, and $23.10. A painting valued at $3.2 million was stolen from the gallery.

Notice that when whole numbers and fractional amounts are used together, ciphers are used after the whole number ($12.00, $3.50).


In general, percentages are expressed in figures followed by the word per-cent. In scientific and statistical material, the symbol % is used.

    • Glenn’s NOW account earns 7 percent interest.
    • There is a 50 percent chance of snow tomorrow.
    • Only 25% of the blood samples tested yielded positive results.
    • Power outages rose by 15% during the summer months.

Fractions and Decimals

Mixed fractions and decimals are expressed in figures. For clarity, decimal fractions of less than 1.00 may be preceded by a zero.

    • 24 1⁄2 feet by 34 1⁄4 feet
    • up to 2.25 centimeters
    • a ration of 0.56 (or .56)
    • the CPI rose 1.5 percent

If several decimal fractions are used in a sentence or paragraph, make sure they have the same number of places to the right of the decimal point.



The variable rates for January were .75 percent, .4 percent, and .96 percent.

The variable rates for January were .75 percent, .40 percent, and .96 percent.

Simple fractions are expressed in words. If the fraction is used as an adjective, it is hyphenated. If it serves as a noun, it is two words.

    • one-fifth share of the market
    • two-thirds majority
    • one tenth of their income
    • one quarter of the workers


In scientific and many business texts, physical quantities such as distances, lengths, areas, volumes, pressures, weights, and the like are expressed in figures whether they are whole numbers or fractions.

    • 125 miles
    • 450 volts
    • .32 centimeter
    • 98.6° Fahrenheit
    • 87 meters
    • 4 pounds
    • 10 ounces
    • 10° of arc
    • 60 acres

In ordinary text matter, fractions may be written out. However, where fractions and whole numbers appear together, use figures to express both numbers.

    • The stadium is about three quarters of a mile from the highway.
    • Give me a sheet of paper 8 1⁄2 by 11 inches.
    • She ordered another box of 3 1⁄2-by-5 1⁄2-inch cards.

If abbreviations or symbols are used for the unit of measure, the quan- tity should be expressed in figures.

    • 3 3⁄4 mi.
    • 25 MPH
    • 5 by 7
    • 6 V
    • 32 g
    • 10%-15%
    • 35mm film
    • 30 cc
    • 36°30 N


Temperature is expressed in figures with the degree sign plus the scale being used.

    • 15° F (Fahrenheit)
    • 20° C (Celsius or centigrade)
    • 12° K (Kelvin)

Parts of a Book

Generally, major book divisions are expressed in Roman numerals and minor divisions in Arabic figures. However, follow the style used in each book.

    • The material in Part I, Chapters 6 through 8 covers how to refinance your house.

Plates, figures, tables, pages, and so on are also set in Arabic figures. The only general exception to this rule occurs in the preliminary or introductory pages of a book, which are usually set in Roman numerals.

    • Be sure to read pages i-ix before starting Chapter 1.
    • Plate 7 in Chapter 23 provides an excellent illustration of a genetic sequence.
    • I don’t think figure 3.1 is accurate.
    • He has the final numbers for tables 2-4.

Inclusive Numbers

Use the following guidelines for inclusive numbers. (The examples are page numbers, which do not require commas.)

  1. For numbers less than 100, use all digits. (4-23; 86-92)
  2. For 100 or multiples of 100, use all digits. (500-563)
  3. For 101 through 109 (and multiples of 100), use only the changed digits. (101-4; 503-6; 1006-9)

  4. For 110 through 199 (and multiples of 100), use two digits or more as needed. (112-24; 467-68; 1389-91; 14285-389)

Continued numbers other than pages are written in the following style:

    • the winter of 1980-81, but the winter of 2000-2001 (when the century changes, use all four digits)
    • the years 1234-1345
    • fiscal year 1984-85
    • AD 712-14
    • 243-221 BC (All digits are used with BC years.)

When an inclusive date is used in a title, all digits are usually repeated.

    • Brian Gregory’s Journals: 1745-1789
    • World War II: 1939-1945