Numbers in Writing: When to Spell Out and When to Use Digits

General Rules for Numbers

One of the most frequently asked questions in English writing is: should I write "7" or "seven"? The answer depends on which style guide you follow and the context of your writing. However, most guides agree on a fundamental principle: small numbers are spelled out, and large numbers are written as digits.

The exact dividing line varies. The two most common rules are:

• Spell out one through nine; use digits for 10 and above (AP Stylebook, APA Style)
• Spell out one through ninety-nine; use digits for 100 and above (Chicago Manual of Style)

Both systems are widely accepted. The key is to choose one and apply it consistently throughout your document. Visit dictionary.wiki for more guidance on English writing conventions.

Style Guide Comparison

The AP and APA rules (spell out 1–9) are simpler and more commonly used in business, journalism, and general writing. The Chicago rule (spell out 1–99) is preferred in book publishing and literary contexts.

When to Always Spell Out Numbers

Regardless of which style guide you follow, certain situations always call for spelled-out numbers:

Beginning of a Sentence

Never start a sentence with a numeral. Either spell out the number or restructure the sentence:

Incorrect: 250 people attended the conference.

Correct: Two hundred fifty people attended the conference.

Also correct: The conference drew 250 attendees.

Indefinite and Rounded Numbers

• There were hundreds of complaints.
• She has thousands of followers.
• About a dozen people volunteered.

Two Numbers Adjacent to Each Other

When two numbers appear next to each other, spell out one to avoid confusion:

Confusing: She bought 12 4-inch nails.

Clear: She bought twelve 4-inch nails.

Common Expressions

• the Four Horsemen of the Apocalypse
• the Twelve Apostles
• zero tolerance

When to Always Use Digits

Some contexts always require numerals, regardless of the number's size:

Addresses

• 123 Main Street, Apartment 4B

Page Numbers, Chapters, and Sections

• See page 7 for details. Chapter 3 covers this topic.

Technical and Scientific Writing

Numbers in scientific contexts are almost always written as digits for precision and readability.

Scores and Voting Results

• The team won 3–1. The motion passed 7 to 2.

Exact Figures in Statistics

• The survey included 3,457 respondents.

Dates and Times

Dates

Use digits for dates in most contexts:

• American format: January 15, 2025
• British format: 15 January 2025
• Numerical: 1/15/2025 (US) or 15/01/2025 (UK/international)

Note the significant difference between British and American date formats—this is a common source of confusion in international communication.

Times

• The meeting starts at 3:30 p.m.
• We arrived at noon (or 12:00 p.m.).
• The event begins at 8 o'clock.

Decades and Centuries

• the 1990s (not 1990's — no apostrophe)
• the twenty-first century (spelled out in most non-technical writing)
• the '90s (apostrophe replaces omitted digits)

Money and Currency

• Exact amounts use digits: $5.99, £10, €200
• Round or approximate amounts can be spelled out: "about fifty dollars"
• Large amounts use a combination: $4.5 million, $12 billion
• Do not use both a symbol and the word: $100 or 100 dollars, not "$100 dollars"

Percentages and Statistics

Most style guides recommend using digits with percentages:

• The approval rating dropped to 42 percent. (AP style: spell out "percent")
• The approval rating dropped to 42%. (APA/scientific style: use the symbol)

At the beginning of a sentence, spell out both the number and "percent":

Forty-two percent of respondents agreed.

Measurements and Units

Use digits with units of measurement:

• The table is 6 feet long.
• Add 2 tablespoons of sugar.
• The temperature reached 95°F.
• The building is 200 meters tall.

In technical and scientific writing, abbreviate units: 6 ft, 200 m, 2 tbsp.

Large Numbers and Approximations

For very large numbers, use a combination of digits and words for readability:

• $3.2 million (not $3,200,000 in general writing)
• 7.8 billion people on Earth
• 1.5 trillion dollar deficit

Commas in Large Numbers

Use commas to separate groups of three digits in numbers of four or more digits:

• 1,000 (one thousand)
• 25,000 (twenty-five thousand)
• 1,234,567

Exceptions: years (2025, not 2,025), page numbers, addresses, and serial numbers do not use commas.

Hyphens with Numbers

Numbers interact with hyphenation rules in several ways:

Compound Numbers

Hyphenate spelled-out numbers from twenty-one through ninety-nine:

• twenty-one, thirty-five, fifty-eight, ninety-nine

Numbers as Compound Modifiers

When a number and a unit form a compound modifier before a noun, hyphenate them:

• a 10-minute break
• a 200-page book
• a five-star hotel
• a three-year plan

Fractions

Hyphenate fractions used as modifiers:

• a two-thirds majority
• a one-half share

Consistency Within a Passage

One of the most important rules is consistency. If a sentence or paragraph contains numbers both above and below your threshold, use digits for all of them to maintain readability:

Inconsistent: The team has three designers, five developers, and 12 managers.

Consistent: The team has 3 designers, 5 developers, and 12 managers.

However, if the numbers refer to different categories, you can mix styles:

The 12 participants completed three rounds of testing.

Here, "12" and "three" refer to different things (people and rounds), so mixing is acceptable.

Common Errors

Error 1: Starting a Sentence with a Numeral

Incorrect: 15 people were injured.

Correct: Fifteen people were injured.

Error 2: Inconsistency in a Series

If comparing numbers in the same category, use the same format for all.

Error 3: Apostrophe in Decades

Incorrect: the 1980's

Correct: the 1980s

Error 4: Redundant Currency Notation

Incorrect: $50 dollars

Correct: $50 or 50 dollars

Summary and Key Takeaways

• Follow your style guide: AP/APA spell out 1–9; Chicago spells out 1–99.
• Never start a sentence with a numeral.
• Always use digits for dates, times, addresses, page numbers, percentages, and measurements.
• Use digits + words for large numbers: $3.2 million, 7.8 billion.
• Hyphenate compound numbers (twenty-one) and number-unit modifiers (10-minute break).
• Maintain consistency within a sentence or paragraph when comparing numbers of the same type.
• No apostrophe in decades: the 1990s, not 1990's.

For related topics, see our guides to hyphenation rules, capitalization rules, and abbreviations and acronyms.