When to use an en dash vs. an em dash

Among the most common problems I see when proofreading for my clients is confusion over the en dash and the em dash. Oftentimes, the confusion is so great that inconsistent styles are used within a manuscript.

First, some definitions:
• En dash – This dash is longer than a hyphen and often about half the length of an em dash (though modern computers’ font options are differ and usually make this only an approximate), or the length of a capital N. Also called an “n dash,” “n-rule,” or “nut,” the en dash typically is used in a closed set of values, such as, “The score was 21–7.” You usually make an en dash on a computer keyboard by hitting the hyphen key and then a return.
• Em dash – This dash is typically twice the length of an en dash, or the length of a capital M. Also called an “m dash,” “m-rule,” or “mutton,” the em dash usually is used to show an idea that is set apart, such as “A character’s passions, desires and fears allow for conflict–and hence your plot–to occur.”

And now comes a whole new set of problems. No one really can agree how the spacing should appear after an em dash. “The Chicago Style of Manual” says no spaces should appear before or after an em dash, as in the above example. Canadian and United Kingdom typography organizations and publishing houses tend to prefer spaces around an en dash.

Confounding this is that software and computer engineers could care less about the issue. Because of this, there’s no key for an em dash on most computers. In addition, typographically the justification of text across a line sometimes makes text appear odd when the em dash connects two words. Spell checks aren’t happy with it, either.

I propose that like “who” and “whom,” the en dash and em dash are increasingly irrelevant and that a simplification of the rules is necessary. Unless an editor or a publisher specifically suggests following a specific format (such as “The Chicago Style of Manual”), I typically edit en dashes in closed sets of values to be a hyphen. When setting ideas apart, I replace the em dash with an en dash, and to make the justified lines more readable, add spaces before or after the em dash.

Call me a heretic, if you must. But most readers (let alone authors) don’t know the difference between an en dash and an em dash. Readers do know, however, when a line is typographically difficult to read. And if your publisher or editor doesn’t like it, she always can change it.

Whichever approach you use, though, always be consistent in its application.
My name is Rob Bignell. I’m an affordable, professional editor who runs Inventing Reality Editing Service, which meets the manuscript needs of writers both new and published. I also offer a variety of self-publishing services. During the past decade, I’ve helped more than 300 novelists and nonfiction authors obtain their publishing dreams at reasonable prices. I’m also the author of the 7 Minutes a Day… writing guidebooks, four nonfiction hiking guidebook series, and the literary novel Windmill. Several of my short stories in the literary and science fiction genres also have been published.