Updated August 31, 2026

5 SAT Comma Rules (With Guided Examples to Boost Your Score)

Bonus Material: 15 Essential SAT Grammar Rules

Commas are everywhere on the SAT. Around 10% of SAT Reading & Writing questions focus on punctuation, and since commas can be used in so many different ways, chances are a lot of those questions will be testing your knowledge of commas rules.

That means that when you’re aiming to boost your score, comma rules are a good place to start.

We’ve used our two decades of experience preparing students for the SAT to line up the 5 essential comma rules you’ll need on the SAT.

First, grab your free copy of the 15 Essential SAT Grammar Rules at the button below, including all the comma rules we’ll dive into in this post. 

Then, below, you’ll find a breakdown of everything you need to know about commas, plus guided examples of real SAT comma questions that show you these strategies in practice.

Jump to section:
The 5 Essential SAT Comma Rules
Comma Rule #1: Use a comma plus FANBOYS to join two complete sentences
Comma Rule #2: Use a comma to join a complete sentence to an incomplete sentence
Comma Rule #3: Use a comma to add a phrase before or after a complete sentence
Comma Rule #4: Use two commas (or two dashes) to insert a phrase in a complete sentence
Comma Rule #5: Use commas to separate items in a list (usually!)
SAT Comma Traps to Avoid
Next steps

The 5 Essential SAT Comma Rules

Before we dive into the details of all the SAT comma rules, here are the 5 essential rules all in one place. 

Comma Rule #1: Use a comma plus FANBOYS to join two complete sentences

Comma Rule #2: Use a comma to join a complete sentence to an incomplete sentence

Comma Rule #3: Use a comma to add a phrase before or after a complete sentence

Comma Rule #4: Use two commas (or two dashes) to insert a phrase in a complete sentence

Comma Rule #5: Use commas to separate items in a list (usually!)

Jot down these rules to keep on hand while you do SAT practice questions – or, even better, download our free, one-page guide summing up every essential SAT grammar rule.

Now let’s dive into how to apply these rules on the SAT.

Comma Rule #1: Use a comma plus FANBOYS to join two complete sentences

FANBOYS on the SAT? No, we’re not talking about your favorite band. FANBOYS is a way to remember the 7 conjunctions that can team up with a comma: for, and, nor, but, or, yet, so. 

A comma followed by one of the 7 FANBOYS words can join 2 complete sentences to each other.

If you need a refresher on how to recognize complete sentences, check out our post breaking it down in detail. In a nutshell, these are the main features that a complete sentence must have:

  • A subject
  • A verb
  • A complete idea

Here’s an example of a comma plus FANBOYS joining 2 complete sentences:

I was already running late, so it was annoying that the bus was delayed.

And here’s an example of what not to do. “Running late yet again” is not a complete sentence: it can’t stand alone.

Running late yet again, so I was annoyed that the bus was delayed.

Tip: If you’re not sure whether something is a complete sentence, check whether it can stand alone by putting a period after it. If what you end up with doesn’t make sense standing alone, then you’re not looking at a complete sentence, and a comma + FANBOYS is not the right way to join it to another sentence.

Ready to apply this rule to a real SAT question?

Detroit natives Timothy Paule and Nicole Lindsey have combined their two passions, Detroit and beekeeping, to improve the health of their city’s flowers and other vegetation. In 2017, the couple converted a vacant lot in the city into an _____; in the years that followed they acquired nine additional lots and established more than 35 hives.

Which choice completes the text so that it conforms to the conventions of Standard English?

A. apiary,
B. apiary, and
C. apiary and
D. apiary

Source: SAT Educator Question Bank

Since this is a punctuation question, we can ignore the first sentence entirely. We’re only interested in punctuating the second sentence.

What are the two pieces of text we’re joining?

  • the couple converted a vacant lot in the city into an [apiary]
  • in the years that followed they acquired nine additional lots and established more than 35 hives

Can each of these sections stand alone?

The couple converted a vacant lot in the city into an apiary.

In the years that followed they acquired nine additional lots and established more than 35 hives.

Both sections can stand alone, so we’re looking at joining 2 complete sentences. One way to do that is by using a comma plus FANBOYS, which is answer choice B.

Check your work by substituting the answer back into the question:

The couple converted a vacant lot in the city into an apiary, and in the years that followed they acquired nine additional lots and established more than 35 hives.

That works!

There are several ways to join 2 complete sentences. A comma plus FANBOYS is just one of them. (For the others, check out our dedicated post on that topic.)

Since this post is about comma rules, we won’t get into all the other methods here, but the key thing to know is that you’ll never have to choose between 2 correct answers.

There will only ever be one correct answer choice on any SAT question. That means that if you’re looking at joining 2 complete sentences, and a comma plus FANBOYS is one option, then you don’t need to worry about choosing between that and another correct answer.

That’s one of those SAT test-taking strategies that are key for success on the test. One of the best ways to work on your SAT strategy is to get guidance from an experienced tutor, so if you’re aiming to take your score to the next level, consider giving our team a call for a free consultation.

Comma Rule #2: Use a comma to join a complete sentence to an incomplete sentence

So what about joining a complete sentence and an incomplete sentence?

There’s really only one way to do that: with a single comma. (There’s no need for a FANBOYS conjunction here – and, in fact, it would be incorrect to use one). 

Let’s look at an example: 

After he published his ground-breaking research; the professor discovered a flaw in his methodology.

Is this sentence punctuated correctly? To check, start by splitting the sentence into two clauses.

  1. “After he published his ground-breaking research” can’t stand alone as a sentence. It starts with the word “after,” which means that it doesn’t express a complete idea by itself: we need to know what happened after this.  We can label this as an incomplete sentence.
  2. The professor discovered a flaw in his methodology, however, can stand alone as a sentence. It has a subject, a verb, and a main idea. We can label this as a complete sentence.

Since we’re joining an incomplete sentence to a complete one, we just want a comma–no FANBOYS conjunction.

After he published his ground-breaking research, the professor discovered a flaw in his methodology.

Time to try this rule on a real SAT question!

About 70,000 meteorites have been found on Earth. Although most meteorites are fragments of _____ hundred have been identified as being from the Moon or Mars.

Which choice completes the text so that it conforms to the conventions of Standard English?

A. asteroids. Several
B. asteroids, several
C. asteroids; several
D. asteroids: several

Source: SAT Educator Question Bank

We can ignore the first sentence, because it’s not part of the sentence that we’re being asked to punctuate. Moving on to the second sentence, start by splitting it into clauses and identifying them.

  1. Although most meteorites are fragments of asteroids

This clause cannot stand on its own. It starts with a subordinating conjunction, so it’s not a complete sentence by itself: it doesn’t express a complete idea. We can label it an incomplete sentence.

  1. several hundred have been identified as being from the Moon or Mars.

This clause has a subject, a verb, and a main idea. It can stand alone. (Without context, we wouldn’t know that “several” refers to asteroids, so it wouldn’t make that much sense – but it would be grammatically correct, which is all we need to know.) We can label it a complete sentence.

So, now we know that we need to join an incomplete sentence with a complete one. That means we want a single comma.

There’s only one option for joining these clauses, which means we can predict the answer before even looking at the choices. Of all the answer choices, only B could work. 

Comma Rule #3: Use a comma to add a phrase before or after a complete sentence

We know that you can join an incomplete sentence and a complete sentence using a single comma. The same goes for adding a phrase before or after a complete sentence: use a single comma.

What’s the difference between a phrase and an incomplete sentence? Since you’ll use commas in the same way for both, we won’t go into it in detail here. The main thing to know is that phrases don’t have a subject or a verb (which incomplete sentences still do).

Here’s what that looks like:

Fluttering to the ground, the pages fell from his hand. (phrase + complete sentence)

The pages fell from his hand, fluttering to the ground. (complete sentence + phrase)

Let’s see this comma rule in action on an official SAT practice question:

Archaeologists have estimated that the pre-Columbian Native American city of Cahokia, located across the Mississippi River from modern-day St. Louis, Missouri, had as many as 20,000 inhabitants in the year 1150 _____ it one of the largest cities in North America at the time.

Which choice completes the text so that it conforms to the conventions of Standard English?

A. CE making
B. CE. Making
C. CE, making
D. CE; making

Source: SAT Educator Question Bank

What we’re interested in here is how to join the final section to what comes before. How can we label “making it one of the largest cities in North America at the time?”

This fragment cannot stand alone, and it lacks a subject and verb. That’s how we know it’s a phrase.

The part that comes before the phrase is a complete sentence (check this for yourself! Can you add a period after it?).

To add a phrase after a complete sentence, all we need is a comma, so answer choice C is what we’re looking for.

Comma Rule #4: Use two commas (or two dashes) to insert a phrase in a complete sentence

A phrase can also come in the middle of a complete sentence instead of before or after it.

To test whether you’re looking at a phrase interrupting a complete sentence, try crossing out the information that comes in the middle of the sentence. If the sentence is still grammatically complete without it, the part you crossed out was a phrase. 

The pages, fluttering to the ground, fell from his hand. (complete sentence with phrase  in the middle)

The pages, fluttering to the ground, fell from his hand. (complete sentence)

A phrase that interrupts the sentence should be set off with two commas (or two long dashes), never just one.

That’s because of this golden rule:

The subject and the verb can be separated by 0 commas or dashes or by 2 commas or dashes, but never by just 1.

You can check that for yourself in the examples above.

Here, the subject and verb of the complete sentence (in bold) are separated by two commas:

The pages, fluttering to the ground, fell from his hand. (complete sentence with phrase in the middle)

How could this rule be tested on the SAT? Here’s an official College Board practice question:

When particles are suspended in liquid (like pollen in a water glass), they will zigzag randomly through the liquid and collide with one another in perpetuity. This type of random, continuous _____ is known as Brownian motion, can be observed throughout the natural world.

Which choice completes the text so that it conforms to the conventions of Standard English?

A. movement: which
B. movement, which
C. movement which
D. movement. Which

Source: SAT Educator Question Bank

We can ignore the whole first sentence here, because it doesn’t affect the punctuation of the second sentence, which is what this question is about. That leaves us with this:

This type of random, continuous movement which is known as Brownian motion, can be observed throughout the natural world.

The first step is to identify the sentences and phrases in this sentence.

  1. This type of random, continuous movement … can be observed throughout the natural world.

How do we know that this goes together? “This type of random, continuous movement” isn’t a complete phrase or clause by itself. The subject is “this type of random, continuous movement.” The verb that goes with this is “can.” “Which is known as Brownian motion” is additional information that’s not part of this clause. Once we’ve removed that addition, we get a clause with a subject, verb, and complete idea, which we can label as a complete sentence.

  1. which is known as Brownian motion

This is additional information inserted into the complete sentence. To confirm that it’s not essential to the sentence, try crossing it out. You’ll see that the sentence still makes sense without it.

Remember that a subject and verb can only be separated by zero commas or by two, never just by one. Knowing that, we’ll need a pair of commas to separate the additional phrase from the complete sentence: answer choice B.

This type of random, continuous movement, which is known as Brownian motion, can be observed throughout the natural world.

Notice that answer choice C would leave us with only one comma between the subject and the verb, which is not an option.

Comma Rule #5: Use commas to separate items in a list (usually!)

Some comma questions involve punctuating lists of items.

If the sentence names only two items, you don’t need any punctuation between them (and, in fact, you shouldn’t use any!). Just the word “and” is enough.

If the sentence lists three or more items, then you’ll usually want to separate them with commas.

On our road trip, we passed through Missouri, Kansas, Nebraska, and South Dakota.

The comma before the final “and” is called the Oxford comma, and it can be controversial! Use of the Oxford comma varies by region, so you may or may not be used to seeing and using it. On the SAT, though, you should always use the Oxford comma.

The exception to this comma rule is when one or more of the list items contains a comma. In that case, you’ll want to use semicolons, not commas, to separate the list items.

On our road trip, we passed through Mansfield, MO; Independence, KA; Walnut Grove, NE; and De Smet, SD.

Try applying this comma rule to a real SAT practice question from the College Board.

In 2018, a team of researchers led by Dr. Caitlin Whalen compiled every available measurement of ocean mixing rates from the past two decades. With this novel data set, the team was able to determine how current-driven mixing varies across ____ and what impact it has on the distribution of heat and nutrients in the ocean.

Which choice completes the text so that it conforms to the conventions of Standard English?

A. regions,

B. regions:

C. regions;

D. regions

Source: SAT Educator Question Bank

This is a list, so you need commas between each item, right?

Nope! This question is slippery – because each item is so long, it gives the illusion that you’re looking at a long list with several items. In fact, you’re looking at only two items:

  • how current-driven mixing varies across regions
  • what impact it has on the distribution of heat and nutrients in the ocean

Since there are only two items, you don’t need any punctuation to separate them. Answer choice D is correct.

SAT Comma Traps to Avoid

The 5 situations above are when you’ll want to use a comma on the SAT. So when should you make sure not to use a comma?

Here are some common SAT comma traps to watch out for.

Trap #1: Avoid the comma splice.

Whatever you do, do not just put a comma between two complete sentences.

This is called a comma splice, and it leads to a run-on sentence, which you don’t want.

This is one of the most common pitfalls when it comes to punctuation rules, and it’s a common incorrect answer choice offered on the SAT. This example shows a comma splice:

The pioneering botanist decided not to embark on the planned expedition to the Amazon due to her health issues, she sent one of her graduate students to take her place. 

Instead of a comma splice, you should use a comma plus FANBOYS here.

The pioneering botanist decided not to embark on the planned expedition to the Amazon due to her health issues, so she sent one of her graduate students to take her place. 

Trap #2: Never put just one comma between a subject and its verb. 

Remember the rule we saw earlier: The subject and the verb can be separated by 0 commas or dashes or by 2 commas or dashes, but never by just 1.

So, if you see a question on the SAT that has a single punctuation mark between subject and verb, first check if there’s a phrase inserted into a complete sentence. In that case, you need a second punctuation mark on the other side of the phrase, and it should be the same punctuation mark (a comma, a long dash, or a parenthesis).

If there’s no inserted phrase and there’s just a random punctuation mark inside the sentence, then the right choice is no punctuation. You don’t need it!

Trap #3: Don’t set off essential information between two commas. 

We saw above that you can set off nonessential information within a sentence by using two commas. The key word here is nonessential.

If the sentence would not be grammatically correct without the information, then it should not be separated with punctuation. Take this sentence adapted from a real SAT question:

The field of geological oceanography owes much to American geologist Marie Tharp, a pioneering oceanographic cartographer. 

 You might be tempted to set off “Marie Tharp” with two commas:

The field of geological oceanography owes much to American geologist, Marie Tharp, a pioneering oceanographic cartographer.

But this wouldn’t be correct, because “Marie Tharp” isn’t extra information – it’s essential for the sentence to be grammatically correct. To confirm this, see what happens when you cross out the phrase:

The field of geological oceanography owes much to American geologist a pioneering oceanographic cartographer.

This clearly doesn’t make sense. 

In short: if you can’t remove a phrase and still have the sentence make sense, then the information is essential and should not be set off between punctuation.

This might sound like a lot of rules to remember–but don’t panic. Like all standardized tests, the SAT is highly predictable, and the more you practice, the more efficient you’ll get at recognizing these transition types.

And because our SAT tutors have been specifically trained for the new digital SAT, they’ll be able to teach you to recognize and solve each type of transition question. Contact us today to get paired with an expert tutor!

Next Steps

These guidelines will help you approach all of the comma-related questions you’ll see on SAT Reading & Writing. But don’t forget about the other question types! Check out our post on the 2 sections of the SAT to find out more about what kinds of questions you can expect across the test.

And if you’re looking for more personalized help to take your SAT score to the next level, reach out to get paired with one of our expert tutors, each of whom has been trained specifically for the new digital SAT.

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Ro

Rosamond graduated summa cum laude from Princeton. During college, she worked as a peer tutor for Italian, French, Greek, and academic writing. Since graduation, she’s continued to tutor students of all ages in French, Italian, Latin, English, and math, some of them for several years. She’s currently a graduate student studying the relationship between religion and secular law, and she works as a freelance journalist and translator.

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