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A period ends a complete sentence that provides a statement or instruction, which is a straightforward function. However, things get a little more complicated when authors have to decide where to place periods after quotations, what spacing to use after a period, and when not to use a period.

Inside or outside punctuation with quotations

Confusion regarding whether a period should appear inside or outside closing quotation marks is usually caused by conflicting styles between American and British authors. The American style presents the period inside the quotation marks, whereas the British style places the period outside the quotation marks (Chelsea, 2011, para. 3). According to the APA Style rules:

  • Use internal punctuation: The closing period should appear inside in the quotation marks (para. 3); e.g., most participants chose “yes.”
  • If the quoted text is a direct quotation of 39 words or fewer and therefore has a citation after the closing quotation marks, the period appears after the citation (American Psychological Association, 2010, p. 171).
  • If the quotation is 40 words or longer and will be formatted as a block quotation, place the period at the end of the quotation and before the citation (p. 171).

For more information on the APA Style rules regarding inside or outside punctuation, please refer to “Punctuating Around Quotation Marks” from the APA Style Blog.

Spacing after a period

In the body of your work, you can use either one or two spaces after a period, but please do so consistently; see Spaces after a period? for more information. To check for consistent spacing, take advantage of Microsoft Word’s grammar and style check, which will look for one or two spaces between sentences:

For instructions on turning on Word's grammar and style check, please see Help From MS Word: Grammar and Style Check.

Within references, a period should always be followed by one space (American Psychological Association, 2010, p. 87).

When not to use a period

According to the APA Style rules, periods should not be used in the following instances:

  • After a URL “to prevent the impression that the period is part of the URL. This is not a style issue but a retrieval issue” (American Psychological Association, 2010, p. 192). This logic would also apply to not providing a period after a DOI.
  • After “metric or nonmetric measurement abbreviations” (p. 88) (e.g., cm, min). Use a period when abbreviating inches (in.) because without the period, “in” could be misunderstood (p. 88).
  • After state abbreviations, capitalized abbreviations, or acronyms (p. 88). Following this logic, abbreviations for Canadian provinces should not be followed by a period.


American Psychological Association. (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: Author. 

Chelsea, L. (2011, August 11). Punctuating around question marks [Blog post]. Retrieved from

Fogarty, M. (2013, December 23). How to use quotation marks [Blog post]. Retrieved from