Numbers in words

Small slips with number words - missing hyphens, mixed numerals and words, wrong ordinals, or singular/plural mismatches - make sentences look careless and can confuse readers. Below are clear rules, focused examples, and quick rewrite templates you can use for work, school, and casual writing.

Quick answers

Be consistent. Hyphenate compound modifiers before nouns, use correct ordinal endings, and make nouns agree with counts. Pick a style and apply it across a document.

Use the same format for numbers that appear in the same sentence or list: either all digits or all words.
Hyphenate spelled-out compounds (twenty-one) and number+unit modifiers before a noun (a 10-page report → a 10-page report or a ten-page report).
Write ordinals with the correct suffixes (1st, 2nd, 3rd) or spell them out: first, second, third.
Pluralize nouns counted by numbers: two cats, five hours.

Core rules at a glance

Keep these four checks in mind: consistency, hyphenation, agreement, and style. If other numbers in the document are digits, prefer digits for clarity. If a number phrase modifies a noun, hyphenate it.

Consistency: match numbers in the same sentence or parallel list.
Hyphens: form single modifiers before nouns (a three-year plan, a 250-word abstract).
Agreement: pluralize counted nouns; watch phrases like "the number of students is" vs "a number of students are."
Style: follow your chosen manual for edge cases like dates, ranges, and percentages.

Wrong: I have 5 cats and three dogs.
Right: I have five cats and three dogs.
Wrong: The report includes 17 charts and twenty-seven tables.
Right: The report includes 17 charts and 27 tables.

Hyphenation: compound numbers and modifiers

Hyphenate spelled-out compound numbers from twenty-one to ninety-nine (twenty-one, sixty-three). Hyphenate number + unit when it modifies a noun before that noun. Do not hyphenate when the phrase follows the noun.

Before a noun: hyphen (a five-year plan). After a noun: no hyphen (the plan lasts five years).
Digits + unit as a modifier get hyphenated: a 5-year-old child.

Wrong: twenty two people attended the meeting.
Right: twenty-two people attended the meeting.
Wrong: She is a 10 year old engineer.
Right: She is a 10-year-old engineer.
Wrong: I need twenty five dollar bills.
Right: I need twenty-five dollar bills.
Work - Usage: We hired a five-person team to tackle the project.
School - Usage: Please submit a 250-word abstract with your paper.

Spacing mistakes: hyphen vs space

People often replace hyphens with spaces or leave hyphens where spaces are correct. Use a hyphen to glue words forming a single modifier before a noun; use spaces when the number phrase follows the noun or stands alone.

Wrong: a 10 year old boy arrived late.
Right: a 10-year-old boy arrived late.
Right after the noun: The boy is 10 years old (no hyphen).
School - Usage: Write a 250-word abstract for the class assignment.
Casual - Usage: She left the interview after three hours.

Ordinals, dates and suffixes

Use 1st, 2nd, 3rd, 4th, etc., or spell out first, second, third. Many style guides prefer dates without suffixes (July 2 rather than July 2nd). Choose one approach and use it consistently.

Irregulars: first, second, third. After that, -th is typical.
Check institutional or publisher style for dates in formal documents.

Wrong: The 2th of July is our meeting date.
Right: The 2nd of July is our meeting date.
Wrong: My birthday is on July 1st, 1990.
Right: My birthday is on July 1, 1990.
School - Usage: Chapter 2 explains the first experiment and its results.

If you want to test a sentence in context, paste the whole sentence into a checker rather than isolating the phrase. Context usually clarifies the correct form.

Plurals and agreement with number words

When a number counts discrete items, use the plural: two cats, five hours. If the number is part of a unit label, follow your unit style: 20 kg or a 20-kg sample (as a modifier).

Wrong: I have two cat.
Right: I have two cats.
Wrong: The number of participants are increasing.
Right: The number of participants is increasing.
Work - Usage: Please review the 3-page executive summary before the meeting.

Digits vs words: choosing a style

Use numerals for data-heavy text, technical content, dates, money, and measurements. Use words in narrative when your style guide requires it. The most important rule is internal consistency.

If a sentence mixes large counts and small narrative numbers, rewrite so formats match.
When numbers begin a sentence, either rewrite the sentence or spell the number out.

Wrong: The sales team reported that Q3 revenue grew by twelve percent and 3 new clients were added.
Right: The sales team reported that Q3 revenue grew by 12 percent and 3 new clients were added.
Work - Usage: Please review the 3-page executive summary and send feedback by Friday.
School - Usage: There are twenty-three students enrolled in the lab section.
Casual - Usage: I'll be there in twenty minutes - see you soon!

Rewrite help: quick fixes and templates

Fix numbers fast: (1) find every number; (2) choose digits or words for the sentence; (3) hyphenate modifiers before nouns; (4) fix ordinals and plurals; (5) read aloud and adjust for flow.

Template A (uniform digits): convert all numbers in the clause to digits for clarity.
Template B (modifier hyphenation): hyphenate number+unit before a noun.
Template C (sentence-start numbers): rewrite the sentence to avoid beginning with a numeral.

Rewrite:
Original: Project requires a 10 page report due 2 days.
Rewrite: The project requires a 10-page report due in two days.
Rewrite:
Original: He finished twenty five tasks this week, impressive.
Rewrite: He finished twenty-five tasks this week - impressive.
Rewrite:
Original: 50 students attended the session.
Rewrite: Fifty students attended the session. (or) The session drew 50 students.
Rewrite:
Original: I have 5 cats and three dogs.
Rewrite: I have five cats and three dogs.

Memory tricks and similar mistakes to watch for

Mnemonic: "Hyphen hugs when numbers help" - if the number helps identify or limit a noun (acts as a modifier), the hyphen 'hugs' the words together. Watch related errors like fractions, currency, and age styles.

Check fractions and ranges: one-third, 3-4 (or 3-4 depending on style).
Decimals vs words: 0.5 vs one-half; be consistent within a document.
Currency formatting: $5 vs five dollars - pick one format and stick with it.

Wrong: He scored ninety five percent on the test.
Right: He scored ninety-five percent on the test.
Casual - Usage: She has two-year-old twins and a three-year-old dog.

FAQ

Should I write numbers as words or digits in a formal report?

Follow your style guide. Business and technical reports usually use digits for clarity (measurements, stats, money). Academic guides differ: APA uses digits for numbers 10 and above; other manuals spell small numbers out. Most important: be consistent.

Do I hyphenate ages and measurements?

Hyphenate ages and measurements used as modifiers before a noun: a 5-year-old child, a three-mile run. Do not hyphenate when the phrase follows the noun: the child is 5 years old; the run was three miles.

How do I write ordinal dates correctly (2nd vs 2)?

Use 1st, 2nd, 3rd, etc., or spell out first/second/third. Many style guides prefer dates without suffixes (July 2). Pick one convention and apply it consistently across the document.

Can I mix numerals and words in the same sentence?

Avoid mixing. If you must, rewrite so all numbers match (all digits or all words) or break the sentence into two to prevent confusion.

What's a fast way to check hyphens and number agreement?

Read the number phrase as an adjective: if it directly modifies a noun, hyphenate. Confirm the noun is plural when counted. For speed, paste the sentence into a checker for suggested hyphenation and agreement fixes, then apply the small rewrite templates above.

Want a quick check?

If you're unsure about hyphens, ordinals, or mixing digits and words, paste one or two sentences into a checker for suggested fixes and a rewrite example.

A quick scan will catch missing hyphens, wrong ordinals, and mixed formats so your writing reads consistently and professionally.