Deciding whether to put a comma before or after but in a sentence is hard for a lot of writers, but it doesn’t have to be for you!
When do you need a comma before but?
You should put a comma before but only when but is connecting two independent clauses.
How do you know you have two independent clauses? First, look at the words before but: I would go for a walk. Then look at the words after but: it’s raining outside. Both of those phrases could stand alone as complete sentences. That means they’re independent clauses, so you need to use a comma before but.
When you don’t have two independent clauses, leave the comma out.
This time, but is connecting an independent clause to a dependent clause. How do you know? Look at the words after but: for the rain. That phrase can’t stand by itself as a complete sentence, which means it’s a dependent clause. Therefore, you shouldn’t use a comma before but.
Examples of when you should and shouldn’t use a comma before but in a sentence
By the way, this comma rule applies to all conjunctions, including and, or, and so.
Do you need a comma after but?
If you’re wondering whether you need a comma after but, the answer is that you probably don’t.
The only time you need a comma after but is when it is immediately followed by an interrupter. An interrupter is a little word or phrase that interrupts a sentence to show emotion, tone, or emphasis. You should always use a comma before and after an interrupter.
In the sentence above, of course is an interrupter. You could take it out of the sentence without losing any meaning. The only reason it’s there is to emphasize the obviousness of the statement. If your sentence happens to place an interrupter directly after but, then go ahead and use a comma. Otherwise, you don’t need a comma after but.