Hyphens, Em Dashes, En Dashes—Everything You Need to Know

by | Sep 18, 2017

I read on a grammar blog recently that “…the em dash is named after its length—it’s about the same width as the capital letter M.”

This is a common error that arises from the fact that in many fonts, the capital “M” is the widest letter, often the same width as the em dash.

However, the em dash—technically, a printing term—has nothing to do with the width of a capital “M,” it’s based on an entirely different and dynamic measurement: the point side of the typeface itself.

So for a typeface being set in 12 point, an “em” is 12 points wide, and so is an em dash. If you change the type to 14 points, the em changes to 14 points as well. An em is simply the horizontal measure exactly corresponding to the type size.

You can see why the “capital letter M” method isn’t logical in this example of two capital letter “M”s from two different fonts. The em dash in both instances is exactly the same width, even though the capital “M”s are very different:

book typography

Now that you understand this very old printer’s measurement, we can dive into the three types of dashes commonly used in written works. To make sure we’re all on the same page, here are each of the three marks under discussion, each next to the letter “a” to provide a point of reference:


In the normal course of things, your editor will be correcting any errors in dash use and indicating where each type of dash should be used. For instance, a manuscript might come back with markups like these:
Because self-publishers are responsible for everything that ends up in their books, you need to know what each of these characters means, the differences between hyphens, en-dashes and em-dashes, and how to get them into your book in the right way.

Varieties of the Dash Experience

Hyphen—As the Chicago Manual of Style (CMOS) says, the hyphen “connects two things that are intimately related, usually words that function together as a single concept or work together as a joint modifier.” Examples include op-in, tax-free, one-third, and so on. Hyphens are very common in English, and the hyphen key is easy to find on the keyboard. The problem with hyphens arises when they are used where another mark—the en dash or em dash—might be more appropriate.

How to insert a hyphen in any program: Just hit the hyphen key on your keyboard, it’s on the top row between “0” and “=.”

En Dash—According to CMOS, en dashes (which are half the length of the em dash) “specify any kind of range, which is why they properly appear in indexes when a range of pages is cited (e.g., 147–48)” and this is also true for date ranges like the period 1948–1960.

In Word for PC, press [Ctrl+Minus] using the minus key on the numeric keypad. In Mac or PC you can also use the Insert/Advanced Symbol/Special Characters dialog and just pick it from the list. But easiest on Mac is the simple key combination [Option–hyphen].

Em Dash—That’s the long dash, and as Grammarist says, “Em dashes set apart parenthetical phrases or clauses in a sentence. In this use, em dashes are similar to commas and parentheses, but there are subtle differences. For example, em dashes are used when a parenthetical remark contains an internal comma or would otherwise sound awkward if enclosed by commas. Perhaps a useful way to think of the em dash is as a pause or parenthesis with somewhat more emphasis than a comma and somewhat less than parentheses.”

In Word, use [Ctrl+Alt+Minus] using the minus key on the numeric keypad or, again, use Advanced Symbols from the Insert menu, and then select Em Dash from the Special Characters tab.

In Word, typing two hyphens in a row will convert into an em dash, and that makes it a lot easier to use.

If you’re working in Adobe InDesign, on Mac you can use the shortcuts listed above, and on any version of InDesign you should also be familiar with the Type/Insert Special Characters/Hyphens and Dashes because you’ll get a whole list of characters you can use as well as your em and en dashes.

Em Dash Spacing

There is some disagreement about the way to employ the em dash. While I’ve always used the dash without any space around it, many other people place a space before and after the dash.

According to The Punctuation Guide, “Most newspapers — and all that follow AP style — insert a space before and after the em dash.”

Did you see that they snuck those spaces into their own quote? Here’s the difference between an em dash with no spaces and one with them:


Of course, this will introduce the possibility of having a line break just before the em dash, and that’s not a good solution. In InDesign or similar layout programs, you could add a “non-breaking” space, then the em dash, then a normal space to make certain the line would never break without the em dash attached to the text preceding it, but that’s a lot of work.

Although these are small punctuation marks, they can make a big difference in how enjoyable your book is for readers, and how well it conforms to standard book typography.

For both these reasons, it’s worth it to keep your hyphens, en dashes, and em dashes straight. If you’d like to know more, use the resource links below.


The Grammar Diva: The Long and Short of It: Dashes and Hyphens
The Punctuation Guide: Em dash
The Chicago Manual of Style Online: Hyphens, En Dashes, Em Dashes
Grammarist: Em dash (Em rule)
Grammarly: Em Dash: Why Should You Love It?

tbd advanced publishing starter kit


  1. Chuck Jackson

    When I discovered using em dash I read as you indicated to put a space before and after the character. When my manuscript was edited, the individual suggested I remove the space. In fact, he didn’t like the use of em dash. I like using them to put emphasis on the dialogue or action. I avoid using exclamation points. This being said, is putting space or leaving it out both acceptable? Thanks.

    • Sharon Goldinger

      Chuck, I love a good em dash. As the Chicago Manual of Style describes their use: “to set off an amplifying or explanatory element.” In that sense they can function as an alternative to parentheses, commas, or a colon. There should be no spaces used around an em dash. Your editor is correct.

  2. Karl Drinkwater

    PS One of the keyboard shortcuts above is wrong (as I found out on testing – but thanks for the Em Dash shortcut, I hadn’t known that variant!)

    It says:

    “En Dash: In Word for PC, press [Ctrl+Alt+Minus] using the minus key on the numeric keypad.”
    “Em Dash: In Word, use [Ctrl+Alt+Minus] using the minus key on the numeric keypad”

    For the En Dash you don’t press Alt, just Ctrl+Minus. Thanks again!

    • Joel Friedlander

      Thanks, Karl, fixed it.

  3. Karl Drinkwater

    There are also often differences between US and UK usage. For example, in the UK we usually have a spaced en-dash, rather than an unspaced em-dash. (For both usages see Hart’s Rules 204, pp86-87.)

    • Joel Friedlander

      Karl, that’s helpful, thanks for letting us know about UK usage.

      • Karl Drinkwater

        Thansk to you for clarifying this topic for writer-publishers. The correct definition about point size, not letter width, was one of the new things I learnt (and I see your explanation is backed up by Hart’s Rules).

  4. Anil

    Thanks. Finally understood the 3. Beautifully, succinctly, and with illustration you have explained.

    • Joel Friedlander

      Anil, thanks for reading, glad it helped.

  5. David Bergsland

    The biggest problem for me is the strange character changes when moving from Word to InDesign. I often have to Find/Change and replace whatever character Word used into the character used in InDesign. It seems to be an encoding issue.

    Also a hyphen is commonly shorter than an en-dash, slanted a little and a bit higher above the baseline.

    • Joel Friedlander

      Thanks, David. Most of the hyphens I’ve examined closely are slanted on the ends of the stroke, although the hyphen itself seems parallel to the baseline.

      And yes, those strange characters and codes Word drops into files are a real pain to get rid of, no matter how much you play with the Import settings.

      • David Bergsland

        You’re right, Joel. I tend to put the happy slant on mine [a la oldstyle e] and forget that’s just part of my style.

  6. Jan Sikes

    GREAT information! Thanks for sharing.

  7. JJ Toner

    I’ve noticed a lot of authors leave no spaces before and after the mdash. This treatment–invariably–can cause formatting problems on eBooks, as the software treats the mdash and its surrounding two words as one word, and has difficulty fitting it on one (justified) line. I prefer to leave a space before and after to avoid these problems. Is this grammatically wrong?
    Are there different rules for the UK? It seems the ndash is widely used in preference to its longer cousin over here.

    • Michael W. Perry

      I’ve not noticed that problem with ereader formatting, but given the general ugliness of how they display text, what you say would not surprise me.

      One fix would be to insert a tiny hair space on each side of that m-dash. That should be treated as a space in formatting a line. For quite a few fonts, the results look better with that space.

      My suggestion would be to write without those hair spaces and use search & replace to insert them only when the book is virtually done. That’ll save time. Do it as the same time your doing other clean up work like striping out double spaces.

      Also, on Macs, a shift-option-[hyphen character] will insert a m-dash. It is so easy and works with almost any app, that I wouldn’t bother with anything else.

      • David Bergsland

        Hair spaces and thin spaces are fixed spaces, just like en and em spaces. So, they shouldn’t break. Of course, I have no idea how Word does things.

        For readability, break after the em-dash, and don’t break the ranges using the en-dash.

        • Joel Friedlander

          I had forgotten to add a section on spacing, which I’ve now done along with another illustration. My “house style” is to never space around em dashes, and that’s how I do all my books. The spaces just seem unnecessary, since the dash is so long already.

          • David Bergsland

            I agree with you, Joel. But the massive nasty arguments I’ve heard over the years boggle the mind.


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