missing hyphen in '2 mile race'

Short rule: when a number plus a unit forms a single adjective before a noun, join them with a hyphen-write a 2-mile race, not a 2 mile race.

Don't hyphenate when the phrase follows a verb or stands alone as a measurement: she ran two miles; the race is 2 miles long. Below are clear rules, copy-paste fixes, rewrite templates for work, school, and casual contexts, and quick checks you can apply now.

Quick answer

Hyphenate number + unit when it directly modifies a noun: a 2-mile race, a 5-page report, a 10-year plan. Do not hyphenate when the phrase follows a verb or is a free measurement: she ran two miles; the report is five pages long.

Before a noun → hyphenate (2-mile race).
After a verb or as a measurement → no hyphen (ran two miles).
No spaces around a hyphen. Use an en dash for ranges (2-4 miles) or write "between 2 and 4 miles."

Core explanation: why the hyphen

The hyphen links a number and unit so they act as a single adjective. Without it, readers can stumble or misread which word the number modifies.

When number + unit comes before a noun, join them as a compound modifier to show they describe the noun together.

Compound modifier before noun → hyphen (a 3-hour meeting).
Predicate or standalone measurement → no hyphen (The meeting lasted 3 hours).

Wrong: She ran a 2 mile race.
Right: She ran a 2-mile race.

Hyphenation rules for numbers, units, fractions, decimals, and ages

Hyphenate most number + unit compounds used adjectivally: 4-foot table, 2-hour meeting, 10-year plan. Hyphenate fractions and decimals when they function as adjectives: a two-thirds majority; a 2.5-hour exam.

Ages follow the same idea: hyphenate before a noun (a 3-year-old child) but not after a verb (The child is 3 years old).

Fractions before a noun → hyphenate (a three-fourths majority).
Decimals before a noun → hyphenate (a 2.5-hour test).
Ages: hyphenate before noun, not after verb.
Plural forms: hyphenate and pluralize the final element when needed (16-year-olds, 5-page essays).

School - Wrong: We scheduled a 2.5 hour exam.
School - Right: We scheduled a 2.5-hour exam.
Wrong: The child is 3-year-old.
Right: The child is 3 years old.

Spacing and dashes: hyphen versus en dash and spacing rules

Hyphens are tight connectors with no spaces (2-mile). Do not insert spaces around hyphens or separate the number and unit with a space. For numeric ranges, prefer an en dash with no spaces (2-4 miles) or spell it out.

If you can't insert an en dash, using a hyphen for ranges is acceptable if consistent, but never add spaces.

Hyphen: no spaces (2-mile).
Range: use an en dash with no spaces (2-5 miles) or write "between 2 and 5 miles."
Avoid spacing errors like "2 -mile" or "2- mile."

Wrong: She prepared for a 2 -mile race.
Right: She prepared for a 2-mile race.
Wrong: The range is 2 - 5 miles.
Right: The range is 2-5 miles or between 2 and 5 miles.

Grammar edge cases and exceptions

Do not hyphenate when the phrase follows a verb or functions as a measurement. Don't hyphenate adverb + adjective combinations when the adverb ends in -ly. Style guides vary on some marginal cases-when in doubt, rewrite for clarity.

Predicate position → no hyphen (The project is two weeks late).
Adverbs ending in -ly + adjective → no hyphen (a highly regarded scientist).
Complex adjectives or multiword units → consider rewriting to avoid awkward hyphenation.

Work - Wrong: The project is running two-weeks behind schedule.
Work - Right: The project is running two weeks behind schedule.
Wrong: She is highly-regarded in her field.
Right: She is highly regarded in her field.

Try your own sentence

Test the whole sentence instead of the phrase by itself. Context usually reveals whether the phrase is a compound modifier or a standalone measurement.

Examples: wrong/right pairs you can copy and paste

Change the numbers or units as needed and apply the same hyphenation pattern.

Work - Wrong: We have a 2 month deadline.
Work - Right: We have a 2-month deadline.
Work - Wrong: This is the 10 year plan.
Work - Right: This is the 10-year plan.
Work - Wrong: She signed a 3 month contract.
Work - Right: She signed a 3-month contract.
School - Wrong: He turned in a 5 page essay.
School - Right: He turned in a 5-page essay.
School - Wrong: We have a 2.5 hour exam tomorrow.
School - Right: We have a 2.5-hour exam tomorrow.
School - Wrong: They ran the 100 meter dash yesterday.
School - Right: They ran the 100-meter dash yesterday.
Casual - Wrong: She ran a 2 mile run this morning.
Casual - Right: She ran a 2-mile run this morning.
Casual - Wrong: I bought a 6 pack of soda.
Casual - Right: I bought a 6-pack of soda.
Casual - Wrong: We took a 10 minute walk after lunch.
Casual - Right: We took a 10-minute walk after lunch.

Rewrite help: quick fixes and templates

If a compound looks awkward or you're unsure, rewrite. Rewrites remove ambiguity and work in speech as well as writing.

Move the measurement after the noun or verb: "a report of four pages" or "the report is four pages long."
Spell out numbers in casual text if it reads better: "two-mile" → "two miles."
Use "between X and Y" or an en dash for ranges instead of forcing a hyphen.

Rewrite:
Original: We need a 2 month update. →
Rewrite: We need an update in two months.
Rewrite:
Original: She ran a 2 mile race. →
Rewrite: She ran two miles.
Rewrite:
Original: The 2.5 hour exam was long. →
Rewrite: The exam lasted two and a half hours.
Rewrite:
Original: The 6 pack deal ends tomorrow. →
Rewrite: The six-pack deal ends tomorrow.

Real usage and tone: formal vs casual

In formal writing-reports, academic papers, client emails-use hyphens consistently for compound modifiers. In casual messages people often skip hyphens, but consistent hyphenation improves clarity even in informal contexts.

When speaking, prefer rewrites that avoid ambiguity since you can't show a hyphen in speech.

Formal: follow hyphenation rules strictly.
Casual: hyphens are optional for speed but recommended for clarity.
Speech: rephrase to avoid ambiguity (say "a race of two miles" or "a two-month deadline").

Usage: Formal email: "Please review the 3-page summary." Casual text: "I'll send the 3 page summary later." (hyphenate in formal writing)

Similar mistakes to watch for

Fixing hyphens often surfaces other small errors: incorrect hyphenation with -ly adverbs, using hyphens instead of en dashes for ranges, and pluralization mistakes in compound nouns.

Do not hyphenate adverb + adjective when the adverb ends in -ly (highly regarded).
Use an en dash for numeric ranges (2001-2005), not a hyphen.
Pluralize compound constructions correctly: 16-year-olds (not 16-years-olds).

Wrong: She is a well respected author.
Right: She is a well-respected author.

FAQ

Do I write "2 mile run" or "2-mile run"?

Write "2-mile run" when the phrase comes before the noun. If you state how far someone ran after the verb, write "she ran two miles."

Should I hyphenate "two weeks late" in "the project is two weeks late"?

No. In that sentence the phrase follows the verb and is not a compound modifier. You would hyphenate in "a two-week delay."

Is "2.5-hour exam" correct or should I write "2.5 hour exam"?

"2.5-hour exam" is correct when the number + unit modifies the noun. Do not add a space. You can also rewrite: "the exam lasted two and a half hours."

How do I write ranges like "2 to 4 miles"?

Prefer an en dash: 2-4 miles, or spell it out: between 2 and 4 miles. Avoid using spaced hyphens for ranges.

What's a quick checklist to fix hyphen errors?

Checklist: (1) Is number + unit directly before a noun? If yes, hyphenate. (2) Is the phrase after a verb or a standalone measurement? If yes, don't hyphenate. (3) No spaces around the hyphen. If uncertain, rewrite.

Want a quick check?

Paste a sentence into a grammar tool to flag missing hyphens and spacing problems, or use the rewrite templates above to fix sentences instantly.