Some topics in this book will offer you choices. Not this one.
Always put exactly one space between sentences.
Or more generally: put exactly one space after any punctuation.
Here’s a paragraph with one space between sentences:
Now the same paragraph, but with two spaces between sentences:
See the problem? In the second paragraph, the extra spaces disrupt the balance of white space. Multiplied across a whole page, rivers of white space can appear.
And one more time, in a typewriter-style font, the one case where two spaces are tolerable (though still unnecessary):
I have no idea why so many writers resist the one-space rule. If you’re skeptical, pick up any book, newspaper, or magazine and tell me how many spaces there are between sentences.
Still skeptical? You’re not alone. For reasons unclear, this advice provokes unusual controversy. The objections sort out into these major themes:
You made up this so-called rule.
No. One space is the custom of professional typographers and the consensus view of typography authorities. No one has yet shown me contrary authority. For instance—
Robert Bringhurst, The Elements of Typographic Style (version 3.1), p. 28.
James Felici, The Complete Manual of Typography, p. 80.
The Chicago Manual of Style (16th ed.), rule 2.9.
I think two spaces look better so that’s what I’m going to use.
I’m accustomed to seeing two spaces between sentences.
Are you? All the professionally typeset materials you read use one space between sentences.
I learned to type on a typewriter, and at this point I’m physically unable to do anything but type two spaces.
When you moved from the typewriter to the computer, you had to learn to type a carriage return at the end of each paragraph, rather than the end of each line. How is this any different?
Everyone I work with uses two spaces.
A core principle of this book is that your documents are governed by the same rules of typography as any professionally typeset book, newspaper, or magazine. If you agree, then the fact that your colleagues habitually diverge from these rules is irrelevant. If you don’t agree, then you will probably find the rest of this material a bore.
Good arguments can be made for both options.
Except that it’s not a matter of argument. One option has the support of typography authorities and professional practice; the other option does not. The issue is not ambiguous. Like language, typographic conventions do change. Maybe in forty or fifty years, the habit will be different. But that’s a topic for the tenth edition of this book. For now—one space.
How can I change? I’ve been doing it wrong for so long!
OK, no one’s quite said so directly. But most objections I’ve heard to this rule (and others) boil down to inertia. Excuses like this serve only to impede learning and preserve bad habits. If you really want to learn about typography, set them aside and approach the rest of this book with an open mind.
I will, however, endorse one exception to this rule:
My boss said I’ll get fired if I don’t use two spaces.
Then let it go. If you’re trying to instill better typography at the workplace, start with something less provocative. (Perhaps eradicating all caps?) Advocates of typography do best when they lead by example, not by decree.