By Graham FisherA booster seat is the step between a harnessed car seat and the vehicle seat belt alone. This guide covers when a child is ready for one, the two standard booster types, how the belt should fit, and when a child can stop using a booster, based on guidance from the American Academy of Pediatrics (AAP) and the National Highway Traffic Safety Administration (NHTSA).
When to move from a harnessed seat to a booster
The American Academy of Pediatrics and the National Highway Traffic Safety Administration both recommend keeping a child in a forward-facing car seat with a harness for as long as possible. NHTSA says children should stay in that harnessed seat until they reach the top height or weight limit allowed by the manufacturer. The AAP lists three signs that a forward-facing seat is outgrown: the child reaches the top weight or height allowed for the seat with a harness, the shoulders rise above the top harness slots, or the tops of the ears reach the top of the seat. Once any of those limits is hit, it is time to move to a belt-positioning booster seat. For more on the different harnessed seat types, see our guide to infant, convertible, and all-in-one car seats.
High-back vs backless booster seats
According to the AAP, high-back and backless are the two standard types of booster seats. Neither type comes with a harness; both are designed to raise a child so the vehicle’s lap and shoulder belt fit over the strongest parts of the body. Both types reduce a child’s risk of injury in a crash when used correctly.
The key difference is where each type can be used safely. The AAP states that high-back boosters should be used in vehicles without headrests or with low seat backs. Backless boosters can be used safely in vehicles that have headrests and high seat backs. Backless boosters are usually less expensive and are easier to move from one vehicle to another. Some seats that look like high-back boosters are actually combination seats: they come with a harness that can be used for smaller children and later removed for older children who need a booster.
Most booster seats are not secured to the vehicle with the seat belt or lower anchors. They rest on the vehicle seat and are held in place once the seat belt is fastened over the child. However, the AAP notes that some booster models can be secured using lower anchors and a tether along with the lap and shoulder belts. Always check the booster seat manual and your vehicle owner’s manual before installing. If you are working with a smaller vehicle, our article on car seats for small cars can help you check fit.
| Feature | High-back booster | Backless booster | Source |
|---|---|---|---|
| Vehicle requirement | Should be used in vehicles without headrests or with low seat backs. | Can be used safely in vehicles with headrests and high seat backs. | AAP |
| Harness | Does not come with a harness; used with vehicle lap and shoulder belt. (Some high-back models are combination seats that include a removable harness for smaller children.) | Does not come with a harness; used with vehicle lap and shoulder belt. | AAP |
| Portability | Not specified. | Usually easier to move from one vehicle to another. | AAP |
| Value Tier | Not specified. | Usually budget-friendly. | AAP |
| Safety | Both types raise the child so seat belts fit properly and reduce the risk of injury in a crash. | Both types raise the child so seat belts fit properly and reduce the risk of injury in a crash. | AAP |
How the seat belt should fit in a booster
Booster seats must be used with a lap and shoulder belt. The AAP and NHTSA describe the same proper fit: the lap belt should lie low and snug across the child’s upper thighs, not the stomach. The shoulder belt should cross the middle of the chest and shoulder, staying off the neck. NHTSA adds that the shoulder belt should not cross the face. Many booster seats have a plastic clip or guide to help position the vehicle belts correctly; the AAP advises following the booster seat manual for how to use that guide.
If your vehicle has only lap belts in the back seat, a booster seat cannot be used. The AAP explains that lap belts work fine with harnessed seats but are never safe with a booster. In that situation, you can keep using a forward-facing harnessed seat with higher weight limits, check whether shoulder belts can be installed in your vehicle, use a travel vest (check the manufacturer’s instructions about lap-belt use), or consider a vehicle with lap and shoulder belts in the back seat. Do not add extra products unless they came with the seat or are specifically approved by the seat manufacturer. The AAP notes that such products are not covered by any federal safety standards and does not recommend them. For more on what to avoid, read our guide on car seat accessories and safety.
When can a child stop using a booster seat?
A child should stay in a booster until the vehicle seat belt fits correctly without it. The AAP states that this typically happens when a child reaches about 4 feet 9 inches in height and is between 8 and 12 years old. Most children will not fit properly in a seat belt alone until age 10 to 12. NHTSA recommends keeping a child in a booster through ages 8 to 12, until the belt fits as described above.
To check belt fit without a booster, the AAP says the child must be tall enough to sit against the vehicle seat back with knees bent over the edge of the seat without slouching, and must be able to stay in that position comfortably for the whole trip. The shoulder belt should lie across the middle of the chest and shoulder, not the neck or throat, and the lap belt should be low and snug across the upper thighs, not the belly. Even after a child outgrows a booster, the AAP and NHTSA agree that all children should ride in the back seat. The AAP says children younger than 13 years should ride in the back seat, and NHTSA says to keep a child in the back seat at least through age 12. For a broader look at car seat stages, visit our car seats category page.
Safety rules that apply to every ride
Booster seats are not certified for use on airplanes. The AAP notes that most rear-facing, convertible, and forward-facing seats can be used on aircraft if they have the appropriate label, but booster seats and travel vests cannot. For a flight, the AAP says to read the seat’s manual and look for the label stating that it is certified for use in aircraft. See our baby travel gear guide for planning road trips and flights.
The AAP also reminds caregivers never to leave a child alone in a vehicle. Temperatures can become deadly in minutes, and children can be injured by power windows, retracting seat belts, or by knocking the vehicle into gear. Every trip, every time, make sure the correct restraint is used and that the child is properly buckled. Being consistent helps form a lifelong habit of buckling up.
Frequently asked questions
Can my child use a backless booster in a car without headrests?
No. The AAP states that high-back boosters should be used in vehicles without headrests or with low seat backs. Backless boosters are only considered safe in vehicles that have headrests and high seat backs.
What if my car has only lap belts in the back seat?
A booster seat cannot be used with a lap-only belt. The AAP advises using a forward-facing harnessed seat with higher weight limits, checking if shoulder belts can be installed, using a travel vest (following the manufacturer’s instructions for lap-belt use), or considering a vehicle with lap and shoulder belts in the back seat.
When should I switch from a high-back booster to a backless booster?
The AAP guidance on the two types depends on the vehicle. In vehicles with headrests and high seat backs, a backless booster can be used as long as the child still needs a booster and the belt fit is correct. Backless boosters are usually easier to move between vehicles and less expensive, but both types are safe when used in the appropriate vehicle and with a proper belt fit.
For more on choosing and using car seats, see our Car Seats guide.
Sources
- HealthyChildren.org (AAP): Car Seats, Information for Families
- NHTSA: Car Seat Recommendations for Children
About Graham Fisher
Graham Fisher is part of our editorial team and reviews and edits our baby gear guides, checking product details against manufacturer specifications and owner feedback.
