Should You Move Your Toddler to a Booster Seat?

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Many parents wonder if their tall young child is ready for a booster seat, or if there's an age requirement. It's easy enough to check the weight and height limits of various boosters to see if your little one will fit according to manufacturer instructions. But, many parents don’t realize that there is also a maturity requirement to ride in a booster.

Before deciding whether your child is ready to move on from a car seat to a booster, you must first understand the difference between the two. Car seats use a five-point harness to restrain the child. A booster seat uses the vehicle’s seat belt across the child's body as a restraint.

What Is Booster Seat Age?

Booster seat age refers to the age of a child at which they are ready to move from a car seat to a booster seat. The appropriate age is generally at least 5 (even though many boosters start at age 4). However, there is also a weight requirement of at least 40 pounds.

Moving a toddler to a booster seat
Verywell / Brianna Gilmartin

Booster Seat Readiness

If you can safely keep your child in a harnessed car seat for a while longer, do it. The American Academy of Pediatrics recommends that kids use a car seat until they reach the maximum height or weight for that five-point harness. This is usually not until at least age five. Three-year-olds are not ready to ride in a booster seat, even if they fit within the manufacturer's height and weight guidelines.

To sit in a booster seat, children should:

  • Be mature enough to sit properly in the booster for the entire trip (no slouching, no leaning over, no messing with the seat belt)
  • Have exceeded the height or weight limits on their harnessed car seat
  • Ideally, be at least age 5 (even though many boosters start at age 4)
  • Weigh at least 40 pounds (even though there are a few boosters that start at 30 pounds)

Many convertible and harness-to-booster car seats have harnesses rated to hold kids up to 65 pounds. In fact, children in the U.S. today can often stay in a harnessed car seat until age six or beyond. Thanks to advances in car seat safety technologies, four-year-olds that might have been moved into a booster 10 years ago can still safely ride in a rear-facing car seat.

Even fairly tall children can remain rear-facing through toddler years and then switch to a forward-facing harness until kindergarten age. For most kids, even those in the 95th percentile for weight or height, there shouldn’t be a reason to move to a booster before age five.

Should You Wait to Switch?

Any step up in car seats—from rear-facing to forward-facing, from the harness to booster—is actually a step down in safety. The 5-point harness spreads crash forces over more points on a child's body, lessening the potential force any one part of the body must take in a crash.

While some high-back booster seats have a minimum weight of 30 pounds, kids should weigh at least 40 pounds before riding in any booster seat.

From a practical standpoint, parents find that it is easier to keep the child sitting properly when in a car seat than in a booster; in a booster the child can unbuckle themselves more easily than in a car seat. They can also lean and slouch, which is dangerous. They can't do that in a car seat when the 5-point harness is properly adjusted.

The seatbelt cannot protect a child who is not in the proper position. Most children cannot be trusted to sit properly until at least five years old.

Many parents find that their child is actually much older than five before they can be expected to sit still in a booster. If your vehicle has lap-only seatbelts in the rear seats, keep your child in a harnessed car seat as long as possible. Harnessed seats can be installed with a lap-only belt.

Booster seats absolutely must be used with a lap/shoulder belt. Extended harnessing, or using a harnessed car seat with a higher weight limit, is vastly preferable to moving a child into a lap-only seatbelt.​

If you have a pre-2008 vehicle with a lap-only belt in the center, it is important to know that car seats can safely go there but boosters and big kids should not. Boosters and big kids need the protection of a shoulder belt. Therefore, if you need to have a kid ride in the center, make sure to use a car seat with a 5-point harness there.

Determining Car Seat Fit

If you think your child is outgrowing their harnessed car seat, first be sure that you're checking the right signs to judge the fit. Most children outgrow harnessed car seats by height long before they outgrow by weight, particularly with the 65-pound seats. When your child is forward-facing, the harness slots should be at or above the child's shoulders. When the shoulders are above the top slots, it's time to change seats.

A forward-facing car seat is also outgrown by height when the tops of the child's ears reach the top of the car seat shell, unless the manufacturer states otherwise in the instructions. When checking the weight limits of the car seat, and be sure you're looking at the forward-facing harness weight limit, not the booster weight limit (if it is a harness-to-booster seat).

There are many harness-to-booster car seats available today with a higher harness limit that later become booster seats if you're concerned about buying another car seat and then a booster. Look for a car seat with a higher harnessed weight limit and a higher top shoulder strap height. This will allow the seat to be used longer in car seat mode (and likely, but not always, in booster mode too).

The range of car seats available today means no family should struggle to find even a budget model that allows their child to remain safely harnessed to a minimum of age five, and most likely far beyond that.

Still not sure if your toddler is riding safely in the car? Visit a nationally certified child passenger safety technician (find one via SafeKids or the National Highway Traffic Safety Administration) to check the installation and usage of your child’s car seat.

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