Period (Full Stop) Inside or Outside the Bracket?

Brackets and Period (Full Stop) Placement

Does the period (full stop) go inside or outside the closing bracket? This is a common question. Here are the overarching rules:

Rule 1. If the parentheses (i.e., the round brackets) contain a complete sentence, then the period (full stop) for that sentence is placed inside the closing bracket.

For example:

• Lee loves cheese-and-onion pies and eats at least two a day. (On weekends, he routinely eats four.) However, he burns hundreds of calories cycling to work.

Rule 2. If the brackets offer additional information that is not a complete sentence, then the period (full stop) is placed outside the closing bracket.

For example:

• Lee loves cheese-and-onion pies and eats at least two a day (four at weekends). However, he burns hundreds of calories cycling to work.
• Lee loves cheese-and-onion pies and eats at least two a day (four at weekends.) However, he burns hundreds of calories cycling to work.
(This is wrong because the first sentence now doesn't have its own period.)

Printable and Sendable Test

End Punctuation with Brackets Follows Logic

The use of end punctuation with brackets follows logic. If the end punctuation belongs to the text inside the brackets, keep it inside. If it belongs to the text outside the brackets, leave it outside.

More Examples of Periods (Full Stops) with Brackets

Here are some more examples showing period placements with closed brackets:

• Turtles communicate at an extremely low frequency that can only be heard through a hydrophone (a microphone used underwater).
(The text in the brackets is just an expansion of "hydrophone." The bracketed text is not a sentence; therefore, it does not get its own end-of-sentence punctuation. The period is required to end the wider sentence.)
• Percy Spencer invented the microwave while working as a researcher for the American Appliance Company (now called Raytheon). After noticing that the radar set melted the candy bar in his pocket, he had the idea to make a metal box using microwaves to heat food. He received a $2 bonus from the company, but he never received any royalties for his invention. (It was the company that filed the patent.)
(The text "now called Raytheon" is not a sentence. The second set of brackets, however, contains a full sentence; therefore, it needs its own period.)

A Sentence in Brackets within a Sentence

Confusion arises when there is a complete sentence within a sentence (as opposed to afterwards). For example:

• Great white sharks generally hunt by detecting the electrical fields (They can detect less than one billionth of a volt) emitted by the movements of their prey.
• As the wine-growing season in France (we lived in France during my twenties) draws to a close, the festivals start.
(Note the lowercase "w" on "we." You have a choice between uppercase and lowercase.)

If the text inside the brackets is a complete sentence within another sentence, you can omit the full stop for style reasons or, if you can't bide the idea of writing a complete sentence without a full stop, you can leave it in. (This is not recommended as it disturbs the flow of text.) There is a lot of leniency on this. You can even start the sentence inside the brackets with a lowercase letter if you think it helps your flow of text.

There's one more quirk. If the text inside your brackets (regardless of whether it's a full sentence or not) warrants a question mark or an exclamation mark, you must include them with the text inside the bracket. For example:

• I ate a whole pack of chocolate biscuits (is that 24?).
(Note the full stop to end the main sentence.)
• I ate a whole pack (yes, a whole pack!) of chocolate biscuits.

Read more about round brackets.
Read about square brackets. Read more about round brackets.
Read about square brackets.