When is a child ready to use a booster seat?

Posted in: Forward-Facing Seats

What’s the difference between a car seat and a booster?

Let’s make sure we’re on the same page – a booster is a seat where the child sits on it and uses the vehicle’s seat belt as their restraint. A car seat is a seat the child sits in and uses a 5-point harness as their restraint.

Yes, there are seats that can do double duty – starting as car seats and turning into boosters. With these seats if your child is using the 5 point harness then they are riding in a car seat – and if your child is sitting on the child restraint and using the vehicle’s seat belt across them, then they are riding in a booster.

Why do kids need booster seats?

Kids need booster seats to help the seat belt fit properly on the strong, bony parts of their body – their hip bones, sternum, and collar bone – and their body fit properly on the vehicle seat.

The lap belt is the hidden danger. A poorly positioned lap belt is what sends kids to the hospital.

How do boosters work to keep kids safe?

Boosters help the seat belt start and stay on the correct bony parts of the child’s body during normal driving and in a crash.

It isn’t a coincidence that boosters make kids taller. By raising the child up, boosters help the shoulder belt fit properly between the shoulder and the neck. By raising the child up and giving the child a shorter seat pan, the child’s knees can now bend at the edge of the booster. This makes kids much less likely to slouch. Slouching is very dangerous as it puts the lap belt on the belly which can cause very serious injuries to the abdominal organs and spinal cord.

Boosters also have design features that help the lap belt start and stay on the lap during a crash. Many boosters use arm rests to do this. Make sure if your booster has arm rests, that the lap belt always goes under both arm rests.

Boosters that earn a “Best Bet” from the Insurance Institute for Highway Safety are the most likely to provide good lap and shoulder belt fit for typical 4-8 year old kids in almost any vehicle.

What types of boosters are there?

We recommend using a high back booster as often as possible and for as long as possible – as the seat belt typically stays better positioned on the child’s body when in a high back booster since kids don’t tend to lean sideways as much both while awake and while sleeping when in a high back compared to a backless booster. Also a high back booster is more likely to keep the child’s body better positioned and the seat belt on the proper parts of the body during pre-crash maneuvers like swerving and hard braking than a backless booster.

For kids who like to sleep in the car, choosing a high-back booster that has a recline and a well designed head rest can be helpful for not only letting the child sleep better and longer, but also keeping their body better positioned in the seat belt while sleeping. One high back booster we find that is especially good for sleeping is the Maxi Cosi RodiFix.

Great times to bring a backless booster are when it just isn’t practical to bring a high back – like when you are going in a taxi/Uber/Lyft, or are sending your child home from school with a parent who you aren’t sure has an extra booster in their car.

When using any backless booster and some high back boosters – specifically those where the back is somewhat flimsy – the vehicle seat needs to support up to at least the top of the child’s ears to decrease the chance of the child getting whiplash. The vehicle seat refers to either the seat itself or the head restraint (if the vehicle has one there); some part of the vehicle’s structure must support up to the top of the ears. If the seat back is not tall enough, then the child needs a high back booster.

Almost half of kids riding in boosters are making this serious mistake – don’t let your kid be one of them!

Most boosters have “arm rests” – and the lap belt must go under these arm rests to ensure that the lap belt starts and stays on your child’s strong hip bones in a crash and doesn’t go up into the child’s soft belly. Studies show that nearly half of all boosters are misused in the same way – the lap belt is accidentally placed over one or both of the arm rests, which is exceptionally dangerous as now the lap belt is on the child’s belly. For those looking for a high back booster, we love the Maxi Cosi RodiFix as they used design to eliminate misuse – they designed this booster so that it offers great seat belt fit and has no arm rests, making it easier for kids to buckle up properly.

Read your booster’s manual carefully to see where the shoulder belt goes – it usually goes under the arm rest closest to the seat belt buckle, but there are a few exceptions where it goes over the arm rest.

My kid likes to slouch – is this a problem?

Yes! Slouching is VERY dangerous in a car – whether you are a kid in a booster, or a big kid/adult in a seat belt – as slouching pulls the lap belt into the belly – which means all the forces of the crash are on the soft abdominal organs like the kidneys, liver, spleen, intestines, and worst of all the spinal cord rather than on the strong hip bones. Slouching also makes the seat belt very loose, which allows the whole body to move more than it should in a crash – but in particular the head moves a lot farther forward and is much more likely to hit the back of the front seat – which causes both brain and neck injuries.

Do I HAVE to transition my child to a booster once they reach 40 pounds?

No! Many 40 pound children are not mature enough to use a booster seat. If your over-40-pound child is not mature enough to sit properly in a booster – i.e. the child likes to try and lean over to fight with a sibling, pick up dropped toys, hang out the window, play with the seat belt, etc – then this child is NOT READY for a booster seat. This child needs a 5-point-harness that can accommodate a taller, heavier child. Since most kids are too tall (their shoulders reach the top shoulder strap slot) long before too heavy in their forward-facing car seat, choosing a seat with the highest shoulder strap slots will allow your child to use the 5-point harness for longer. The seats that have the highest shoulder strap slots (and both turn into boosters for later on) are the Britax Frontier/Pinnacle Click Tight ($339) and the Chicco MyFit ($199).

My child is too wide to fit in most boosters.

Meet the Safety 1st Incognito – the perfect backless booster for big kids. 

Why shouldn’t my 3 year old 30 pound child use a booster?

The 5-point harness of a forward-facing car seat provides the best protection for pre-schoolers because it not only restricts movement, ensuring that toddlers are in the proper position should a crash occur, but also distributes the crash forces over a larger area of the body when compared to a safety belt and booster seat (two chest straps with the safety seat’s 5-point harness versus one chest strap with the safety belt.). While many booster seats say that they can be used for children weighing as little as 30 pounds, it is best to wait until the child is at least 40 pounds (and has met the other minimums stated above) before using a booster seat.

How long do kids need to ride in a booster seat?

Kids need a booster seat until the seat belt fits properly on their body without the help of a booster (the lap belt is on their lap and the shoulder belt is between the neck and shoulder) AND their body fits properly on the vehicle seat (they can sit back with their knees bent without having to slouch). Studies show that half of all 10 year olds need a booster seat to ride safely – and by 12, almost every child is ready to ride safely without a booster.


42 Responses to “When is a child ready to use a booster seat?”

  1. Jennifer says:

    Our 5 1/2 year old is now 48 inches to 48.5 inches and 44 lbs, and while his car seat accommodates up to 100 lbs forward facing, he is nearing the 49 inch limit to the seat (Peg Perego Primo Viaggio Sip 5-70). He still is “comfortable in his car seat overall, but the top limit of the shoulder straps are soon going to be below his shoulders a little. His head still does “fit” between the headrests pretty well. Must we switch to a booster seat now? He is still a bit squirmy and does fight with his sibling in the car sometimes, since she rear faces in her car seat and we have put him in the center seat for his increased safety riding forward. Thank you for being there for us!!

    • Jennifer – The Peg Perego 5-70 goes to a max of 70 pounds (not 100) OR the child’s shoulders reach the shoulder strap slots when the head rest is in its highest position. Almost every child is too tall long before reaching the 70 pounds. When he outgrows the Peg Perego, if he is not mature enough to sit properly in a booster, you can look into a seat that has higher shoulder strap slots – like the Britax Frontier 90 – to keep him harnessed longer.

  2. Ali says:

    My 2.5 yr old son weighs 47 lbs and is 41 inches tall… We are going away n need a carseat or booster for shuttle to and from hotel only ( we have a britax carseat at home which I’ll continue using) just wondering if 4 yrs is actually a requirement or weight n size are the key factors cuz it would. Be a lot easier for lugging thru airport etc…

    • Age is a key factor as there is no way a 2.5 year old is mature enough to sit still in a booster seat. Please note that kids should be AT LEAST 4y AND AT LEAST 40 pounds AND mature enough to sit properly (no slouching, no leaning over, no playing with the shoulder belt, etc) before riding in a booster. Your 2.5 year old needs to ride in a 5 point harness.

  3. RN says:


    I have a question: we have twin 3-year-old boys and need a second set of car seats to take them to and from school. One of the boys is about 32 pounds (not sure of his height, probably around 37 inches.) Our other son is about 26 pounds and not sure of his height. In the main car, we have Diono Radian convertible car seats, and they still are rear-facing. I was looking into getting the First Years b570 booster as a second set of car seats. I know that our smaller son would need a different seat until he is 30 pounds. (A friend has given us a Britax that her son used.)

    In reading on your site, I see that they probably shouldn’t be in a booster for another year, until they’re 4? Is there a less expensive convertible seat that is as safe as the Diono? (and I don’t think we can fit two rear-facing seats in our second car. It’s a 2004 Volkswagen Jetta.) I also don’t want to have to buy new seats now and then new seats in a year from now.

    Any suggestions you have would be much appreciated.

    • To go into a booster a child should be AT LEAST 4y AND 40 lbs AND 40inches. Your bigger twin is 2 years away from 40 pounds, and the smaller one about 3-4 years away from 40 pounds. The booster is not appropriate for them now or for several more years to come. If you are looking for a long term seat that would also fit rear-facing in your Jetta, take a look at the Graco Milestone.

  4. Amber says:

    I have a 5 year old that weighs 33 lbs and is 39.5″ tall. He is in a five-point right now but it is about to expire and we are thinking of getting him a high back booster. Are we nuts?

  5. Maureen M. says:

    My mother-in-law wants to get car seats for her own vehicle to help my husband and I when picking up and dropping off our 2 2-year-old sons from daycare.
    Our oldest son is about 27 pounds and about 35 inches tall (2 1/2 years old). Our other son who is 2 1/4 years old is about 38 inches tall and about 38 pounds.
    My MIL has been searching for an inexpensive option and has chosen several forward facing seats with a weight limit of 40 pounds, to which I immediately say no.
    She came across a few 5-point harness booster seats.
    Are they safe for my boys at their ages and sizes?

    • A 40 pound weight limit would likely be fine for the 27 pound child – although this child will likely outgrow the seat in his height before reaching 40 pounds. Your 38 pound son is going to need a harness for at least another 3 years or so – and will need a limit well beyond 40 pounds. If she has LATCH in her car, she might want to look into the IMMI Go which will come out in the next 2-3 weeks and sells for $199 and installs very easily with LATCH and can accommodate both boys until they are ready for a booster.

      • Maureen M. says:

        So, for right now they are both too small for a booster WITH a 5-point harness?

      • Maureen M. says:

        Upon further inspection, I’m glad I looked, the booster from Target (the link that I sent you) has a minimum HIGHT requirement which is inches taller than my boys. I’m going to recommend that if my MIL really wants to get something she should get the Evenflo SureRide DLX 65 Convertible Carseat from Target.
        Thank you for your help.

    • The least expensive seat that will last both boys long enough is the Evenflo Sure Ride (but the buckles can be hard to undo – especially for grandparents).

  6. Maria says:

    My son is 6 years old and 43lb,not too tall. He still fits his 5 point harness seats but he has been traveling in one of the cars with a booster and loves that he can buckle himself and feels more comfortable. He sits perfectly in it since we usually use it just for trips to his school 5 min away from our house. Is booster as safe as a 5 point harness? Would it be better to keep him in a 5 point harness longer even for short trips? I would not be using a booster for longer trips for fear he might fall asleep in the car.

    • For kids who are over 4y, over 40 pounds AND able to sit properly in a booster – a booster is a very safe option. I would suggest looking for a high back booster with deep sides that fits him nicely (as he will eventually sleep in it one day).

      • Maria says:

        He is in Graco HB Turbo booster now and it fits him nicely. Would you recomend switching him to a booster in all car seats or trying to keep him in a 5 point harness longer. He has a Graco Neutilus in the other car

        • The Nautilus can turn into a high back booster and would be fine to use. If he sleeps frequently in the car, then I’d keep him in the 5 point harness as he is likely to stay better positioned during sleep in the 5 point harness than in a booster.

  7. Heather says:

    My 6 yo son is 48″ and 58#. He is currently using a 5pt Graco Nautilus. He is mature enough to sit up on his own and not squirm around, but I know the five point is safest and I would like to keep him in it as long as I can. However the seat part of the Nautilis is not deep enough for him anymore and he complains that the buckle portion is digging into his boy parts. Is there a five point harness for older children that has a deeper seat? Or, am I being over protective and should just move him to a booster?

    • I would move him to a booster. We don’t have evidence that a 5 point harness is a safer choice for a child of his age, weight, and maturity level. Boosters have been shown to offer excellent protection when used properly for kids like him.

  8. Ashley says:

    What do you suggest for a child whose shoulders are about to be at or above the straps on their Britax Frontier 90 but aren’t 40lbs yet? My son is 36-37lbs and only 44 inches but all torso, and his shoulders are very very close to the limit. He is 3.25, and very tall.

    • The Frontier 90 has the highest shoulder strap slots of any harnessed seat on the market. I’d make sure that your head rest really is up all the way – and that something isn’t preventing it from going up to the highest positions (I’ve seen this happen on a few occasions where it got stuck and it wasn’t all the way up).

  9. Jody says:

    Do you have a recommended booster seat that is a 5-point-harness to a booster? I am looking to buy a new carseat for my son who is 3 1/2 and start it as a harness seat and transition to a booster so my daughter who is 8 mo can use his convertible?

  10. Erica says:

    My oldest is 5.5 years old and about 44″ tall. He’s outgrown his Britax 5-point in height (head over back shell) but he only weighs about 35 lbs. He’s absolutely ready from a maturing/sitting still point, and I’d rather not buy another 5-point harness for the last 5 pounds (although at this rate he might not weigh 40 pounds until he’s 20). Are there any boosters that are suitable for skinny kids (preferably high-backed)?

    • A forward-facing child’s head can go over the top of the seat, so long as the top of the child’s ears are at or below the top of the shell AND the shoulder straps come from at or above the child’s shoulders. I wouldn’t switch to a booster just yet – but you could get a seat that starts as a 5 point harness and turns into a booster – like the Graco Nautilus with Safety Surround, Graco Argos 80, or Britax Frontier.

  11. Janel says:

    My daughter is 7 and already weighs about 100 lbs. Her hips and thighs are above “average” in width(to give an idea in size she wears 16 in pants) but she is still too short to sit with feet flat on the floor. Her current booster is too narrow for her to sit comfortably in. Could you please give me some ideas of boosters that would accommodate her better.

    • The Safety 1st Incognito would be a great option if your vehicle seat back/head rests support at least to the top of her head. So would the Little Tikes backless booster and the Harmony Carpooler. If she needs a high back booster to provide the needed head support, check out the Britax Frontier or the Little Tikes high back booster (the new Cybex Solution M-Fix will also work well, but won’t be available until spring 2015 or so).

  12. Barbara says:

    My little girl is 3 years old and weighs 58lbs and her carseat straps are getting to tight to fasten and extended all the way. Its a carseat that holds up tp 100lbs.Can she go in a booster?

  13. Megane says:

    I am looking for a safe inexpensive combination seat for my 3 year old daughter. She is currently 30 pounds and was in the britax marathon but her little brother will now be switching from his infant seat to the britax marathon. Could you suggest a combination seat please? I was looking at the eve fly sure ride from previous comments but was wondering if you had other suggestions. Thank you!

  14. Brittany says:

    I have my daughter, 4 years old, in a booster I bought when she was almost 3. She has always sat perfectly in it. Due to her age I was told she needs to be harnessed. But is there a 5 pt. harness she will fit in? Current stats: 4 years, 48″, 52#, and her torso length is 18″. It needs to fit in a Mazda Tribute 04 with 2 other car seats.

  15. Dawn says:

    Our daughter is 4 1/2, weighs 38 pounds and is 41 inches tall. She is Mature and content to sit in her current car seat Britax Boulevard 70 but it is a HUGE pain to get her in and out of the seat as the shoulder straps are snug and she has zero interest in helping to fasten herself. I am unsure the safety of a booster type with 5 point harness compared to a true booster for her. I am Considering the Britax frontier or pinnacle clicktight that begins as a 5 point but can be transitioned to a booster with belt. Would this seat be safe and easier for her to get into and out of and perhaps assist with belting herself? Thoughts?

    • Double check that her straps aren’t snug for the following reasons:
      – She is wearing a coat that is too bulky for the car seat
      – The shoulder straps haven’t been adjusted so that they come from at or above her shoulders

      A car seat with a 5 point harness is a car seat with a 5 point harness… whether it turns into a booster later on doesn’t make it safer or less safe in the 5 point harness mode than another seat that doesn’t turn into a booster. The Frontier & Pinnacle are easier to get the child into as it sits lower and is wider in the inside. However, the head rest on these seats is very high and can be a visibility issue in some cars. Also look at the Graco Nautilus with Safety Surround.

      • Dawn says:

        Thank you! Yes it is very difficult to get the straps over her shoulders when she has on a coat so we usually take the coat off. I will check again to see if I can adjust the shoulder strap any higher but I believe it is in the highest slot. I drive an Acura SUV and her current seat sits rather high in the car so I can’t imagine a new one sitting any higher. :-). Thank you for your input and for sharing your knowledge of all things car seats!

  16. Amanda says:

    Hi. My son will be 3 in February. He’s a big boy. I’d like to keep him harnessed until 5. But I cannot for the life of me, find a seat that harnesses past 65 lbs. Help?

  17. Megan says:

    Can a 5pt. Harness Booster can be used rather than a convertible car seat for a 3 year old/33 pounds?

  18. Suzi says:

    Im looking for a cheap 5 point harness seat that can go past 40lbs. We just got a foster son who is only 3, but weighs 39lbs. He could potentially only be with us a few months so we don’t want to break the bank on a car seat that won’t be used long, but I would feel better if he was in a 5 point harness. Any suggestions?

    • The least expensive seat with the highest harness capacity (very tall in seated height and weight capacity) is the Evenflo Sure Ride. Yes, there are other seats that are less expensive that will claim to accommodate to similar weights, but kids are too tall for these long before the weight limits.