Em dash vs en dash: which one, and when (a writer's rule)

Quick answer. An em dash (—) is the long one, the width of a letter m. It marks a break in thought — like this — or sets off an aside, and stands in for a comma, colon or parenthesis. An en dash (–) is shorter, the width of an n. It means "to" or "through" between numbers and dates (pages 12–20, 1990–1995) and joins two words of equal weight (the New York–London flight). A hyphen (-) is shorter still and joins a single compound word (well-known, self-publish).

Key takeaways

• Em dash (—), longest: a pause or an aside. Use it where a comma would be too weak and a full stop too final.
• En dash (–), middle: ranges (2010–2020, chapters 3–7) and connections between equals (the author–editor relationship).
• Hyphen (-), shortest: one compound word (best-seller, two-thirds, e-book). It is not a dash at all.
• Spacing: US style runs a closed em dash (word—word, no spaces); UK style often spaces it (word — word). Pick one and keep it for the whole manuscript.
• You do not need a keyboard code. Write -- and let your word processor's autocorrect or your editor convert it; just check the type of dash that lands.

The three marks, side by side

The names come from typography, not grammar: an em dash was once the width of a capital M, an en dash the width of an N. That is the only memory hook you need — M is longer than N, so the em dash is longer than the en dash.

When each one is right

Em dash — the break in thought. Use it for an interruption, a dramatic pause, or an aside you want to feel spoken rather than parenthetical:

• He sent the manuscript to three publishers—two said no.
• The cover—the third one, not the first—finally worked.
• A pair of em dashes can hold an aside where parentheses would feel too heavy and commas too quiet.

Do not overuse it. A page with an em dash in every paragraph reads breathless; the dash is a spice, not the meal.

En dash — ranges and equal pairs. Use it for any span from one thing to another, and for two terms that carry equal weight:

• Read pages 40–65 before Monday.
• 2020–2024 were her best writing years.
• The London–Paris train. Here the dash says the two places are linked as peers, not that one owns the other.

Hyphen — the compound word. Use it to join words that act as one unit before a noun, and in numbers, fractions and prefixed words:

• a well-known author, her best-seller, two-thirds done, re-edit, e-book.

The hyphen is the one people actually need most; the dashes are the flourish. If spelling and hyphenation are slipping, that is the tell that the manuscript wants a proofread.

The mistakes that actually happen

• Using a hyphen where a range is meant. pages 12-20 should be 12–20. In a manuscript this looks like a typing slip even when it is a habit.
• Using an en dash for a thought-break. He left – and never returned wants an em dash, or a full stop.
• Mixing spaced and closed em dashes across a manuscript. Choose one convention and apply it everywhere.
• Letting autocorrect decide. Word processors may turn -- into an em or en dash depending on their own settings, and the result can differ from your style sheet. Check, do not trust.
• Spacing before and after a closed em dash. If you use the US closed style, there is no space on either side (word—word). Spaced style is a UK convention; either is fine, but be consistent.

A fast proofreading pass

1. Search the draft for - (hyphen). For each hit ask: is this a compound word, a range, or a break in thought?
2. Ranges and "to" pairs become en dashes (12–20). Thought-breaks become em dashes (—). Compound words keep the hyphen.
3. Check consistency: is every em dash spaced the same way? Is every range using the same dash? A style sheet note is the fastest cure.
4. Read each em dash aloud as a pause. If the sentence does not need the pause, delete the dash and use the comma or full stop it was standing in for.

That pass — dash by dash, plus hyphens, apostrophes and the rest — is exactly what a full proofread covers, chapter after chapter, so the slips do not come back on the next draft. If your manuscript is finished and you want that read, our editing and proofreading service is where it happens.

Related guides

Keep going: how to write a book, the types of book editing, book editing services and proofreading services. For a dictionary definition, see em dash (Cambridge Dictionary).

Disclosure: Harmony Publishing is a self-publishing company and links to its own services where they match a step. The language guidance here is practical, not a rule for every style guide.