How to Use Dashes

There are two kinds of dashes you’re likely to need in your writing—em dashes and en dashes. Neither is the same as a hyphen, so don’t think you can substitute without anyone noticing. An en dash is traditionally the length of a letter n, while em dashes are—you guessed it—the length of an M.

- hyphen
– en dash
— em dash

Cats make great roommates—if you don’t mind the smoking—and terrible landlords.

The Em Dash—An Interruption

The em dash is what most of us think of when we think of dashes—a break in the flow of the sentence. It’s often used as a colon, to introduce or expand on what came before (see Colon vs. Semicolon for more on colons), as in the last sentence and in this section’s heading.

Em dashes commonly work in pairs to set off a word or phrase from the rest of the sentence. They’re a little more emphatic than a pair of commas but a little less off-topic than parentheses.

• Cats make great roommates—if you don’t mind the smoking—and terrible landlords.

In dialogue, a pair of em dashes can make room for an action, and a single em dash can show interrupted or faltering speech. (For more examples, see How to Punctuate Dialogue.)

• “He said he’d be walking the thylacine”—Shareena checked her phone—“right about now.”
• “Whatever you do, don’t push that—”

Occasionally, an em dash follows a word or words that introduce a sentence’s main clause.

• Revenge—that was the sisters’ goal.
• Aliens, spaceships, face-eating fungi—nothing fazed Felipe.

Em dashes are often put before the source of a quotation, though they are not obligatory.

If you can’t say anything nice, come sit by me.

—Dorothy Parker

Revenge—that was the sisters’ goal.

The Dash With Other Punctuation

When a comma, semicolon, or period falls next to a dash, the dash shoulders it off the page. But when a pair of dashes encloses a phrase ending in an exclamation point or question mark, that punctuation can stay.

• Your combat skills are inferior—at least, inferior to mine—but your fashion sense is unrivalled. (No comma before but.)
• Spade unwrapped a black bird—could it be the Maltese falcon?—and casually set it on his desk.
• It’s not like I have a crush on him—as if!—but he does have nice hair.

The En Dash

En dashes are used to express ranges, where you might otherwise write from…to… or between…and…. They can also be used instead of to.

• The average human heart weighs 250–300 grams.
• Randy’s Roller Disco is open Tuesday–Sunday.
• Eartha Kitt played Catwoman in the 1967–68 season of Batman.
• The Rome–Sydney flight was cursed by a jet-lagged strega.
• Our impromptu game of “flaming quidditch” ended in a score of 7–3 and a visit to the ER.

What you don’t want to do is combine en dashes with from or between. Use words or dashes, not both.

• The Countess plans to travel incognito from April 6–May 12. X
• Emile and his imps serve coffee daily from 7:00 a.m. to 4:00 p.m. ✓
• Don’t go near the castle August–October. ✓

• Mastering spatula combat can take between 3–4 years. X
• Improving your diction will require between 10 and 15 marbles. ✓
• Each morning I believe 5–7 impossible things before breakfast. ✓

Eartha Kitt played Catwoman in the 1967–68 season of Batman.

Dashes, Typography, and Spacing

The equivalent of an em dash in typescript--in case you’re stranded on a desert island with only a typewriter--is two hyphens. As for en dashes, you can probably get away with using a hyphen instead—in fact, the Associated Press prefers it. However, there’s no reason to be old-fashioned when you have a computer at your disposal. Programs like Word automatically transform two hyphens--without spaces--into an em dash and a single hyphen - with spaces - into an en dash. (More on this below.) Since computers can’t always read your mind, it’s good to know the keyboard shortcuts:

Mac

En dash: Alt + Hyphen

Em dash: Alt + Shift + Hyphen

Windows (use numeric keypad)

En dash: Alt + 0150

Em dash: Alt + 0151

Should you put spaces around your dashes? Most American style guides, including The Chicago Manual of Style, prefer closed em dashes—that is, em dashes without spaces. But many British publishers use open en dashes – that is, en dashes with spaces – instead, and The Elements of Typographic Style considers the open en dash aesthetically superior to the em dash.

Though the closed em dash is more widely used, both are correct, so the choice is up to you. However, don’t put spaces around your en dashes when they are expressing ranges or to; such en dashes should always be closed.

Your combat skills are inferior—at least, inferior to mine—but your fashion sense is unrivalled.

A final word on dashes—try not to use too many. It may be tempting—they're so handy—but more than one or two per page—three at most—will look choppy and may distract your reader. I am, myself, occasionally guilty of overusing the dash. I have certainly done so in this post—purely for pedagogical purposes, of course.