Style guide5 min read
Em dashes in academic and formal writing
What APA, Chicago, MLA and Harvard actually say about em dashes, whether to space them, and how to handle the AI question in a submission with a policy.
Updated September 25, 2026
How this was tested
Style-guide positions were verified against the current published editions (APA 7, CMOS 17, the MLA Handbook) in September 2026, not against secondhand summaries. The density advice is calibrated with our own counts: the academic-writing post on this blog runs 9.5 em/en dashes per 1,000 words after editing, and one or two per manuscript page is the same order of magnitude.
Numbers last verified:September 25, 2026
The short version
- APA 7 permits the em dash but advises restraint: use it sparingly and do not use spaces around it.
- Chicago permits it, prefers no spaces, and warns that dashes "tend to be overused".
- MLA treats it as standard, unspaced, with restrictions on how many can sit in one sentence.
- British style (and much of Harvard referencing guidance) commonly uses a spaced en dash instead, which is a different character entirely.
Academic writing is the one context where the em dash question has a real, checkable answer, and it is not the answer the internet gives you. No major style guide bans the em dash. Several explicitly tell you not to use many of them, which is a different instruction and a more useful one.
Then there is the second question, which is new: does using one look like AI in a submission that has an AI policy? That one has no style guide behind it, so it is worth separating from the first.
What each style guide says
| Style | Position | Spacing |
|---|---|---|
| APA 7 | Allowed, "use sparingly" as a substitute for commas, parentheses or a colon | No spaces |
| Chicago (CMOS) | Allowed; warns that because dashes are flexible they "tend to be overused" | No spaces, closed up |
| MLA | Standard punctuation; avoid more than one pair in a sentence | No spaces |
| AP (journalism) | Standard and frequent; spaces around the dash | Spaces |
| British / Harvard housestyles | Often a spaced en dash where US style uses a closed em dash | Spaces around an en dash |
Two things follow. First, using an em dash is not an error in any of these systems. Second, the guides converge on the same practical advice: the mark is powerful and therefore easy to overuse, so edit down rather than reach for it by default.
Spaced or unspaced is a house-style question
APA, MLA and Chicago close the em dash up; AP spaces it. British publishing usually swaps it for a spaced en dash. If your department or journal has a template, the template wins over all of this.
Where the dash earns its place in academic prose
In formal writing the em dash has three uses that survive editing:
- A gloss inside a sentence. "The intervention — a twelve-week coaching programme — ran across three sites." Here paired dashes do something parentheses do, with more emphasis.
- A payoff after a full clause. "One variable predicted the outcome — prior attainment." A colon also works; the dash is more dramatic and therefore riskier.
- A break before a qualification. "The effect was significant — in two of the four cohorts." This is the use that most often reads as a style problem in a thesis.
Over-dashed
The sample — drawn from two schools — was small — though representative — and the results — while significant — were modest.
Edited
The sample, drawn from two schools, was small but representative. The results were significant but modest in size.
The AI question in a submission with a policy
Most institutions now have an AI-use policy, and many run submissions through a detector. That creates a practical concern that has nothing to do with grammar: a marker who spots three em dashes may form a hypothesis, and the hypothesis may be wrong.
Two honest observations. Detector scores are unreliable enough that they are not treated as evidence on their own at most institutions, and they disproportionately flag non-native English writers. And a dash habit is a normal thing for a careful writer to have. See how accurate AI detectors are for what the reliability numbers actually look like.
Given all that, the pragmatic move is not to change how you write. It is to be able to show how you wrote: drafts, notes, version history. If you want to reduce exposure anyway, trimming the dash is a two-minute edit that costs you nothing stylistically.
Converting dashes for submission
Which tool you want depends on what the target wants:
| Target | What to do |
|---|---|
| APA, MLA, Chicago | Keep em dashes, remove the spaces around them if you typed them spaced |
| British housestyle or a spaced-en-dash journal | Convert dashes from em dash to en dash, then space them |
| A department that discourages dashes | Replace em dash with a comma, colon or parentheses |
| A PDF-based workflow | PDF em dash remover first, then convert |
Run the em dash counter before and after so you know the density of the final file, and check that a find-and-replace has not broken a page range or a hyphenated term.
Convert the dashes for submission
Swap em dashes for punctuation, or convert between dash types, without editing a word of your argument.
Open the AI dash removerFrequently asked questions
Are em dashes allowed in academic writing?
Yes, in APA 7, Chicago, MLA and most house styles. APA advises using them sparingly, and Chicago warns that dashes tend to be overused. Being allowed is not the same as being encouraged.
Do you put spaces around an em dash in APA style?
No. APA closes the em dash up with no spaces either side. AP style, which is journalism rather than academia, does space it, and British publishing commonly uses a spaced en dash instead.
How many em dashes are too many in a dissertation?
A rough working limit is one or two per page of body text. More than that and the dashes start competing with the argument for the reader’s attention, which is the concern Chicago is describing when it warns about overuse.
Will em dashes make my essay look AI-written?
They can raise a marker\u2019s suspicion, fairly or not, because the character is associated with model output. It is unlikely to matter on its own. If your institution runs detector scores, know that those are unreliable and fix the underlying issue rather than the punctuation.
Should I use an em dash or a semicolon in formal writing?
A semicolon joins two independent clauses neutrally; an em dash joins them dramatically. In formal academic prose the semicolon is usually the safer choice, and the dash is better kept for glossing a term inside a single clause.
How do I remove em dashes from a thesis without changing the argument?
Replace rather than delete: a comma where the dash set off a short aside, parentheses where the aside is longer, a colon where it introduced a list. The replace em dash tool applies the same substitution across a whole document in one pass.
Keep reading
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