The debate over spacing after a period feels surprisingly personal for something so small. In practice, for decades, the standard practice taught in typing classes was two spaces. Today, the Publication Manual of the American Psychological Association (APA) mandates a single space. Practically speaking, understanding this shift is essential for students, researchers, and professionals aiming for polished, compliant manuscripts. The current guideline is unambiguous: APA Style requires one space after a period (or any other punctuation mark that ends a sentence, such as a question mark or exclamation point) Simple, but easy to overlook. No workaround needed..
The Short Answer: One Space, No Exceptions
If you are formatting a paper for a psychology, education, nursing, or social sciences course, the rule is simple. After the period at the end of a sentence, hit the spacebar once. This applies to the body text, the reference list, figure captions, and table notes. On top of that, there are no exceptions for specific sentence structures or abbreviation types within the standard narrative flow. The APA Publication Manual (7th Edition), Section 6.1, explicitly states: "Space once after a period... at the end of a sentence And it works..
Why the Rule Changed: A Brief History of Typography
To understand why APA insists on one space, it helps to look at the technology that created the two-space habit in the first place. The "two spaces after a period" convention originated in the era of monospaced typewriters. Even so, on a typewriter, every character—whether a narrow i or a wide W—occupied the exact same horizontal width. So this created a loose, uneven visual texture. Adding two spaces after a sentence provided a stronger visual cue, helping the reader’s eye distinguish the end of one thought from the beginning of the next It's one of those things that adds up..
Modern word processors (Microsoft Word, Google Docs, LaTeX) use proportional fonts. On top of that, an i takes up less space than a W. In proportional typesetting, characters have varying widths. And because the spacing between words and letters is professionally kerned and balanced by the font designer, the "hole" created by a double space is no longer necessary for readability. In fact, in proportional fonts, two spaces create distracting "rivers" of white space running down the page, interrupting the reading flow.
APA Style, along with virtually every other major style guide (MLA, Chicago, AP), transitioned to the single-space standard decades ago to align with professional typesetting standards.
APA 6th Edition vs. 7th Edition: Clearing the Confusion
A significant source of confusion stems from the transition between the 6th and 7th editions of the manual.
- APA 6th Edition (2009–2019): The manual recommended two spaces after a period in draft manuscripts to aid readability during the review process, but noted that published work used one space. This dual standard caused widespread inconsistency.
- APA 7th Edition (2020–Present): The manual simplified the rule. One space is now required for all manuscripts, whether draft or final. The distinction between "draft" and "final" spacing was removed entirely.
If you are using an older template or advice from a professor who hasn't updated their materials since 2019, you may still see the two-space recommendation. Always follow the 7th Edition standard (one space) unless a specific instructor or publisher explicitly requests otherwise in writing.
Not obvious, but once you see it — you'll see it everywhere.
How to Implement the Rule in Your Workflow
Breaking a decades-long muscle memory habit is difficult. Here are practical ways to ensure compliance without manually deleting every extra space.
1. Use Find and Replace (The Nuclear Option)
Once your draft is complete, use the Find and Replace function (Ctrl+H or Cmd+H):
- Find:
.(Period followed by two spaces) - Replace:
.(Period followed by one space) - Click Replace All.
- Repeat for
?and!. - Pro Tip: Run this twice to catch any instances of three or four accidental spaces.
2. Configure Microsoft Word Grammar Settings
You can tell Word to flag double spaces as errors as you type.
- Go to File > Options > Proofing.
- Under "When correcting spelling and grammar in Word," click Settings next to "Writing Style."
- Scroll down to Punctuation Conventions.
- Set Space Between Sentences to One Space.
- Click OK. Now, a blue (or red) squiggly line will appear under double spaces, allowing you to fix them instantly via right-click.
3. Adjust Google Docs Preferences
Google Docs does not have a native "flag double space" grammar check yet, but you can use Tools > Preferences > Substitutions to create an automatic replacement (though this can be buggy with abbreviations). The Find/Replace method remains the most reliable for Google Docs users Small thing, real impact..
Common Pitfalls and Edge Cases
While the rule is "one space after a period," the definition of "end of a sentence" gets tricky with abbreviations and citations.
Abbreviations (e.g., i.e., et al., Dr.)
Do not add an extra space after the periods inside an abbreviation Which is the point..
- Correct: The study included Dr. Smith et al. (2020) noted...
- Incorrect: The study included Dr. Smith et al. (2020) noted... The period in "Dr." or "et al." is not a sentence-ending period. Treat it as part of the word. Only the final period of the sentence gets the single space.
Citations at the End of a Sentence
This is the most common formatting error in APA papers.
- Correct: The results were significant (Smith, 2020). Next sentence starts here.
- Incorrect: The results were significant (Smith, 2020). Next sentence starts here. The period goes after the closing parenthesis of the citation. You place one space after that final period.
Ellipses (...)
APA 7 uses the three-dot ellipsis character (…) or three spaced periods (. . .) to indicate omitted material within a sentence.
- If the ellipsis ends a sentence, use four dots total (three for the ellipsis, one for the sentence terminator):
.... - Apply the one space rule after that fourth dot.
The Readability Debate: Science vs. Habit
You may encounter arguments claiming two spaces improve reading speed or comprehension. A widely cited 2018 study from Skidmore College (Attention, Perception, & Psychophysics) suggested that two spaces might marginally speed up reading for people who already prefer two spaces. Even so, the effect size was tiny, and the study used a monospaced font (Courier New), not the proportional fonts (Times New Roman, Calibri, Arial) required by APA Practical, not theoretical..
Major readability experts and typographers (like Matthew Butterick, author of Practical Typography) argue that in proportional fonts, double spacing creates visual "holes" that disrupt the horizontal rhythm of the text. APA’s decision aligns with the consensus of the professional publishing industry: consistency and clean texture aid comprehension more than exaggerated sentence gaps.
Accessibility Considerations
Single spacing is also better for accessibility. Screen readers and text-to-speech engines do not "read" spaces; they parse punctuation. On the flip side, for users with cognitive disabilities or those using high-zoom magnification, "rivers" of white space caused by double spacing can make tracking lines of text significantly harder. A uniform, single-spaced text block provides a predictable visual structure that benefits all readers.
Quick Reference Checklist for APA Spacing
Before submitting your paper, run through
