Missing hyphen in 'billion dollar'

Small punctuation choices change meaning. Use billion-dollar when the number+unit modifies a noun; use billions of dollars when you're stating an amount.

Below: concise rules, clear examples for work, school, and casual writing, and quick rewrites you can apply immediately.

Quick answer

Hyphenate number+unit when it forms a compound adjective before a noun: a billion-dollar deal, a ten-year plan. Do not hyphenate when stating an amount after a verb: the deal is worth billions of dollars.

Modifier (before a noun): hyphenate → a billion-dollar investment.
Amount (after a verb): no hyphen → the investment is worth billions of dollars.
If unsure, rephrase: a multi-billion investment or an investment worth a billion dollars.

Core explanation: hyphenation rule for number + unit

When a number (word or numeral) and a unit work together to describe a noun, link them with a hyphen so readers know they act as a single adjective: a million-dollar grant, a 10-year study. If you're simply stating how much or how many-usually after a verb-use the plural noun form without a hyphen.

Before a noun = hyphenate (modifier).
After a verb = no hyphen (amount).
Singular number + singular unit often hyphenated: a one-week trial.

Hyphenating number+unit compounds: numbers, words, and plurals

Spell out small numbers in formal prose or use numerals; both can be hyphenated when they modify a noun: a three-month internship or a 3-month internship. Use the unit in singular form inside modifiers: a two-mile run, not two-miles run. When the amount stands alone, use the plural unit and no hyphen.

Modifier: a 100-page report (use commas in large numerals in formal writing: 1,000-page).
Amount after a verb: The report is 100 pages; The company is worth billions of dollars.
Keep units singular inside modifiers: a five-million-dollar contract.

Spacing and punctuation: where the hyphen sits

Hyphens have no spaces around them. Place sentence punctuation after the phrase as usual. If you add adjectives before the compound, the hyphen remains: a rapidly growing billion-dollar company.

Correct: a billion-dollar valuation.
Incorrect: a billion - dollar valuation.
Move the phrase after the verb to remove the hyphen: the valuation is worth a billion dollars.
If a hyphenated modifier ends a sentence, add the period after the phrase: a billion-dollar idea.

Real usage and tone: formal vs casual

In formal writing-reports, papers, press releases-follow hyphenation rules strictly. In casual messages, readers may infer meaning without hyphens, but published text benefits from precision: a billion-dollar deal reads as a single concept; worth billions of dollars emphasizes total value.

Formal: hyphenate modifiers for clarity and punch.
Casual: omission is common but can create ambiguity.
When tone matters (headlines, resumes), prefer hyphenation.

Work: Headline - Company Secures Billion-Dollar Partnership (hyphenated for clarity).
Casual: Text - They raised billions today (amount, no hyphen).

Try your own sentence

Test the full sentence rather than the isolated phrase; context usually shows whether the expression is a modifier or an amount.

Examples: realistic pairs for work, school, and casual contexts

Each pair shows a common slip and the corrected hyphenated form when the phrase modifies a noun. Replace company, study, or mistake with your own noun to create correct compounds.

Work - Wrong: The team closed a billion dollar deal last quarter.
Work - Right: The team closed a billion-dollar deal last quarter.
Work - Wrong: We landed a 5 million dollar contract with the supplier.
Work - Right: We landed a 5-million-dollar contract with the supplier.
Work - Wrong: The acquisition created billions dollar market value.
Work - Right: The acquisition created billion-dollar market value.
School - Wrong: She wrote about a million dollar experiment in her lab report.
School - Right: She wrote about a million-dollar experiment in her lab report.
School - Wrong: The study describes a three year longitudinal analysis.
School - Right: The study describes a three-year longitudinal analysis.
School - Wrong: He applied for a ten thousand dollar scholarship.
School - Right: He applied for a ten-thousand-dollar scholarship.
Casual - Wrong: I heard about their billion dollar party last night.
Casual - Right: I heard about their billion-dollar party last night.
Casual - Wrong: She told me she got a 2 million dollar bonus.
Casual - Right: She told me she got a 2-million-dollar bonus.
Casual - Wrong: That's a million dollars idea!
Casual - Right: That's a million-dollar idea!

Fix your sentence: three quick rewrite patterns

If you're unsure whether to hyphenate, apply one of these edits: move the amount after the verb, convert to a noun phrase, or use a clear scale modifier.

Move the amount: This project is an opportunity worth a billion dollars (instead of This project is a billion-dollar opportunity).
Convert to noun phrase: a billion-dollar investment → an investment worth a billion dollars.
Use modifiers: multi-billion or near-billion to avoid long compounds when appropriate.

Rewrite:
Wrong: This project is a billion dollar opportunity. →
Right: This project is a billion-dollar opportunity. Or: This project is an opportunity worth a billion dollars.
Rewrite:
Wrong: We achieved 50 million dollar revenue. →
Right: We generated $50 million in revenue. Or: We achieved $50-million revenue.
Rewrite:
Wrong: That's a 1000 page book. →
Right: That's a 1,000-page book. Or: The book runs 1,000 pages.

Memory trick: a short test to decide quickly

Insert the word "worth" between the number and the unit. If this makes the phrase read naturally, don't hyphenate. If inserting "worth" breaks the phrase, the number+unit is likely a modifier and needs a hyphen.

Test: "billion dollar deal" → "billion worth dollar deal" (fails) → hyphenate: billion-dollar deal.
Test: "worth billions of dollars" reads fine → no hyphen needed.
If the test is unclear, rewrite the sentence to make the role of the amount explicit.

Similar mistakes to watch for

Other common hyphenation errors include age phrases (ten-year-old student vs the student is ten years old), compound fractions (two-and-a-half-hour meeting), and unit combinations (full-time employee vs an employee who works full time). Also watch adverb+adjective pairs and prefixes.

Age compounds: a ten-year-old student vs the student is ten years old.
Adverb + adjective: many guides drop the hyphen after -ly adverbs (highly paid, not highly-paid).
Compound fractions and repeated compounds: a two-thirds majority, a two-and-a-half-hour meeting.

Wrong: She is a ten years old student.
Right: She is a ten-year-old student.

FAQ

Do I hyphenate "billion dollar" before a noun?

Yes. Use a hyphen when the phrase modifies a noun (billion-dollar project) to show the words form a single adjective.

Is "The project is worth billion-dollar" correct?

No. After a verb, use worth + plural amount: The project is worth billions of dollars. Use billion-dollar only before a noun.

How do I hyphenate numerals with multiword units like "5 million dollars"?

Hyphenate when the whole number-unit string modifies a noun: a 5-million-dollar contract. If it's an amount after a verb, don't hyphenate: The contract is worth $5 million.

Should I hyphenate numerals like "1000-page"?

Yes: use 1,000-page book when the number modifies the noun. Use comma separators for clarity in large numerals in formal writing.

What's a quick edit to catch these mistakes?

Try the "worth" test: insert "worth" between the number and the unit. If the sentence becomes unnatural, hyphenation is likely needed. For quick scans, paste sentences into a grammar checker that flags missing hyphens and offers rewrites.

Want a second opinion on your sentence?

If a hyphen or rewrite still feels uncertain, paste your sentence into a grammar checker to flag missing hyphens and suggest clear rewrites-e.g., convert "billion dollar investment" to "billion-dollar investment" or "investment worth billions of dollars."