Should You Use One or Two Spaces After a Period?

If you’re here looking for the simple answer to this simple question, here goes:


That was easy, wasn’t it? But, since you probably asked that question because what you were taught before contradicts what you’re being taught now, let me clarify the ins and outs of this particular writing rule.

Trust Me: One Is the Standard

To begin, let’s look to the official rules. This comes from CMOS (i.e., the one style guide that rules them all):

Like most publishers, Chicago advises leaving a single character space, not two spaces, between sentences and after colons used within a sentence [...], and this recommendation applies to both the manuscript and the published work. (Chicago Manual of Style, 16th Edition, section 2.9)

CMOS isn’t alone on this front, either. The Associated Press (AP) very clearly states the rule, and the Modern Language Association (MLA) acknowledges that most presses use one space.

Okay, okay … but why? And why did your teachers tell you to use two spaces?!

How It Used to Be

Remember, the very idea of “spacing” (in the sense we’re referring to it) originated, not with writing, but with typewriting. When you’re writing something by hand, there’s no such thing as uniform spacing—at least if your handwriting is as terrible as mine—so the real point is just to make it clear that the new sentence has started.

In the age of the typewriter, the standard was two spaces after the end of a sentence. Our dear friend Grammar Girl tells us that the reason for the double space is that most typewriter fonts are “monospaced,” meaning that each letter took up the same width on the page. It’s easy enough to see:

This is a monospaced font.
This is a proportional font.

Now, you’ll notice that the period of the monospaced font is quite far out from the final letter of the sentence, at least when compared to the proortional period. Also, dry typewriter ribbons tended to make periods almost invisible. With these shortcomings noted, there was a very good reason to create the extra space: it ensured that the sentence’s conclusion was evident—without having to rely on the period’s placement or even visibility.

The tendency to add two spaces became mainstream in the typewriter’s era, so even after those monstrous writing machines went the way of the Zune, the “rule” of two spaces stayed the same. This was so standard that my two English professor parents taught it to me as a matter of literary law, and that was just less than two decades back. Over time, though, the issue of spacing has been hotly debated, and those debates concluded with the single-space option as the victor.

The Advantages of a Single Space

There are those who point to a single space as having many advantages. “It looks better,” they say. “It improves the sense of sentence flow,” they say. “It prevents readers from getting distracted by the purgatory of an extra blank area,” they say. “It cures cancer,” they say.

Who says all this? Well, passionate typographers, mostly. These are the sorts of people who are preoccupied with how just a couple millimeters of white space will make or break a page. For the rest of us, the real advantages of using a single space boil down to this:

  1. A single space has become the standard, so the second space can look like an error.
  2. Writing in HTML (and thus almost anywhere on the web) automatically removes your second space, which further reinforces the single space standard and makes your attempts at second-spacing useless.
  3. If you don’t use a single space, your editor will probably wind up doing a find-and-replace anyway. Your work will wind up with the solitary space, and your only added benefit is a frustrated editor.

That’s not to say a double space has no advantages. For one, it has an element of clarity in distinguishing the end of a sentence from an abbreviation. For example, “I’ll have a chat with K. Kesler, then, shall I?” may, on a skim, look like two sentences—at least if we’re accustomed to the standard of a single space at the end of a sentence. Further, the double space makes it clear a new sentence has started even if a word is not capitalized. While rare, cases of non-capitalization at the beginning of a sentence do exist. For example, “e.e. cummings” is never capitalized, nor is the “e” of “eBay.”

That said, the double space advantages are few and far between, and even those of us rushing through a read can typically tell when a sentence has ended, abbreviations and e.e. cummings notwithstanding. We might be able to lay the entire thing to rest and just switch over to one space, except …

The Rule Is Not Universal

The MLA has this to say about single spaces after a sentence:

[M]ost publishers’ guidelines for preparing electronic manuscripts ask authors to type only the spaces that are to appear in print.

[...] As a practical matter, however, there is nothing wrong with using two spaces after concluding punctuation marks unless an instructor or editor requests that you do otherwise.

So, according to MLA, you can use two spaces if you damn well please. AP and CMOS disagree. So do most publishers. But this remaining scrap of contested territory mixes blood with the old tradition of adding a second space, and the result is that students are taught different standards. The end of our current path is clear, though: The single space will become universal. You may as well start using it now.

Switching Over to a Single Space

I switched over to a single space toward the beginning of my freelance career, at the request of one of my major clients. I started obsessing over my second spaces, killing them with great displeasure—even with a sense of loss—as I wrote. For several weeks, I had to do a find and replace on every document I wrote because I always left a few extra spaces in.

It took me about a month to break the my second-space habit. It will probably take you about that long as well. I don’t have any grand tips or shortcuts for you: Just keep the standard in mind, delete the second space every time you notice yourself using it, and proof your completed documents to ensure that you have kept to the standard.

Good luck, and write on,

Rob D Young