In typography an <strong>em</strong> equals the current type size and an <strong>en</strong> is half that width, which is why the em dash (—) is the longer one. Use the en dash (–) for ranges and connections — "pages 41–58", "the Dublin–Belfast line" — and the em dash (—) to break a sentence open, where a comma, colon or pair of brackets would also work. The hyphen (-) is shorter than both and only joins words.</p>
Three marks, three jobs
The confusion here is really a three-way one, so it helps to line them up:
- Hyphen (-) — joins parts of words: well-known, twenty-three, re-enter.
- En dash (–) — spans or connects two things: Monday–Friday, the 2010–11 season, the Bakerloo–Victoria interchange.
- Em dash (—) — interrupts a sentence: The report — all 400 pages of it — arrived late.
The names describe width, not shape. In modern digital type an em is defined as the point size in use, so at 12pt an em is 12 points wide; an en is half of it.
The test you can run
Ask what the mark is standing in for.
If it replaces the word to or through, or the word and between two names of equal weight, it is an en dash: 7–9pm reads "seven to nine", the Smith–Jones agreement reads "Smith and Jones".
If it replaces a comma, colon or bracket — marking a pause, an aside or a swerve — it is an em dash: She had one rule — never explain.
If it replaces nothing and simply glues two words together, it is a plain hyphen.
Spacing, and the honest bit about house style
Spacing is a genuine disagreement between conventions, not a right-and-wrong matter. American practice, following Chicago, sets the em dash closed up to the words either side: one rule—never explain. Most British publishing does not use the em dash at all in running text; it uses a spaced en dash instead: one rule – never explain. Both are correct within their traditions. What you should not do is mix them in a single document, or use a spaced hyphen as a substitute in anything typeset properly.
The edge cases
Two details catch people out. First, do not put an en dash in a range you have already introduced with a word: write from 1998 to 2004 or 1998–2004, never from 1998–2004. The same applies to between … and.
Second, use a hyphen, not an en dash, when the two elements are not equal partners. Anglo-Irish takes a hyphen because Anglo is a prefix, but the Ireland–Wales ferry takes an en dash because both places stand alone.
Frequently Asked Questions
Which dash do I use for a date range like 2019 to 2023?
An en dash: 2019–2023. Do not pair it with the word from — either write "from 2019 to 2023" or "2019–2023", never "from 2019–2023".
Should there be spaces around an em dash?
It depends on your style. American convention closes the em dash up to the surrounding words with no spaces; British convention generally avoids the em dash and uses a spaced en dash instead. Be consistent throughout the document.
How do I type an em or en dash?
On a Mac, Option+hyphen gives an en dash and Shift+Option+hyphen gives an em dash. On Windows, use Alt+0150 and Alt+0151, or let your word processor autocorrect a double hyphen.