A few weeks ago, I wanted to write something but no matter how long I stared at my computer, I couldn’t come up with anything interesting to write about. After an embarrassing amount of time, I took to my social media channels and asked my friends what their top car seat question was. I found a lot of commonalities among the things people offered up because there are definitely some areas of car seating that are more difficult than others, but there was a wide variety of things people want to know more about. And after looking through the responses and sitting on it for a bit, I’m going to use those suggestions (and new ones that come along), to launch a new series of articles.

I decided my first “You Asked” post would be whichever topic came up the most from my friends, and the result ended up being one of the questions I get most often in person from friends and family, so it feels right to start here.

You Asked: When is it time to switch to a booster?

I think boosters are confusing because all the seats you’ve used up to this point have been sort of similar. They all install in a relatively similar pattern, the way you secure your child is consistent, but then you get to boosters and they don’t install the same way and they don’t work the same way and it’s just hard to know if you’re doing it right. As a parent who is starting to booster-train for the first time, I feel this confusion first hand.

So let’s start with a little terminology. A booster, or belt-positioning booster, is a car seat that does NOT use a built-in harness, but instead uses the vehicle seat belt to restrain the child. There are products that refer to themselves as a “Harnessed Booster” or “Harness-to-Booster” and we call those types of seats “combination seats” because they combine a forward-facing seat that has a 5-point harness with a booster seat. Those are 2 completely different modes of use. If you are using a combination seat with the 5-point harness for your preschool-age child, that’s perfectly fine. Technically, it’s not a booster (even if that’s what the product name implies) unless you are using it in booster mode without the harness.

Most booster seats (or combination seats used in booster mode) have either a 30 or 40-pound weight minimum, a height minimum and an age minimum of 3 to 4 years, generally speaking. Unlike a harnessed seat, which restrains the child with a built-in 5-point harness, the booster is used to literally boost the child up so that the adult seat belt fits properly on the strongest parts of their body – the pelvic bones and collar bone. A good belt fit means the shoulder belt lays flat across the middle of the collar bone and the lap belt lays across the thighs and off the belly.

Now, I realize I just said that 3-year-olds can use boosters, but I want to stop here and clarify something. While some boosters do not list a specific age minimum, and others list age 3 or 4 as the minimum, it is my opinion that dedicated booster seats are not appropriate for 3-year-old children. I am currently raising my second 3-year-old and I’ve spent a pretty extensive amount of time around 3-year-olds and let me let you in on a secret: they are not known for excellent decision making. They just aren’t. My first child was probably one of the most compliant and calm 3-year-olds and even he lacked the frontal lobe development to make the kind of choices that a booster requires a child to make. Putting your 3-year-old in a booster might be legal in some states and with certain products, but it’s not a great idea unless you don’t have any other options.

I put my current 3-year-old child in a booster for less than 2 minutes to take a picture of him and I told him to sit still. This is a progression of what took place in those 2 minutes and it perfectly illustrates the issue:


Here’s the thing: boosters require maturity in a way that a 5-point harness doesn’t. A 5-point harness holds your child in the safest position without any effort on your child’s part. In a 5-point harness, your child can fall asleep, can reach for something next to them, can do any number of attempted gymnastics and assuming you have installed the seat well and buckled them correctly, they will still be just as safe. A booster, on the other hand, allows the child a lot of freedom of movement. It allows slouching, it allows toppling over when asleep, it allows them to tuck the shoulder belt behind them and it allows them to lean forward to pick toys off the floor, all the things my 3-year-old did in a matter of 2 minutes. But unlike in a harness, all of these scenarios in a booster are seriously dangerous. A booster only works to keep your child safe in a crash when the seatbelt is positioned properly on the child. So, if you can’t trust your child to sit upright for an entire car ride, even when asleep, they shouldn’t be in a booster. Period.

You can safely keep your child in a 5-point harness until they outgrow it by height or by weight, so there’s not a rush, no matter what anyone else is telling you. There’s no evidence (trust me, I’ve looked for it), that keeping a 6 or 7-year-old in a harness (if they still fit) is more dangerous than using a booster. We do know that allowing a young child who lacks impulse control to move to a booster too soon can absolutely be extremely dangerous.

So, you asked when you should you move your child to a booster and the simplest answer is:

In order to ride in a booster, a child must meet the height, weight AND age minimums of their seat AND they must be able to sit upright through an entire car ride with a good belt fit. Provided that your child is still within the height and weight limits of their harnessed seat, keeping a child in a 5-point harness beyond age 4 or 5 is fine and many parents choose to do that. If your child does not have the impulse control to sit safely in a booster seat but they’ve outgrown all the harnessed seat options, there are medical car seats that will allow your child to remain seated safely for longer (see your physician, medical therapists or a CPST near you for more information).


Some other information on boosters can be found here:

IIHS Booster Seat Ratings Bonanza: Where does your booster seat rank?

CarseatBlog recommended high back booster seats

CarseatBlog recommended combination seats