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When should my child move up a car seat stage?

Expert advice on spotting when your child is ready to change car seats

Author Kat Gemmell
Categories   Car Safety

The Edit

There are three stages of car seat that your little one will use throughout their first 12 years.

A baby seat, a toddler seat and finally, a child seat. These will be an infant carrier from birth, a toddler seat with a 5-point harness, then a high-back booster child seat which secures your child with the seatbelt.

You can choose from single stage individual seats such as our Dream i-Size infant carrier or Discover i-Size high-back booster. Or you can opt for a multi-stage seat which covers one or more of the three stages – such as Motion All Size 360 or Balance i-Size.

All seats have minimum and maximum height or weight limits, which are unique to the individual seat. Your child is safest using each seat to the maximum limit rather than jumping up to the next stage as soon as they hit the minimum. 

Not moving up until the maximum limit of the current seat is especially important when you come to make the move from rear facing to forward facing.   

How to tell when a seat is outgrown: 

Harness seats 

Your child has reached the maximum harness weight limit – this can never be exceeded. 

Your child has reached the maximum harness height limit – although this can be exceeded if the child is safely fitting within the harness by height and it can be comfortably fastened (for example, they may have hit the height limit but have long legs, it is the sitting height which is important for car seat harness fit). 

Your child’s eyes are level with the top of the seat shell (for seats without a stated height limit). 

High-back booster seats 

Their shoulders are touching the bottom of the high back booster headrest. 

Reasons they haven’t outgrown their rear facing car seat: 

 We often get asked if a child has outgrown their rear facing car seat because their legs are coming over the end of the car seat. This isn’t a safety or comfort issue at all, and they don’t need moving up a seat stage.   

Rear facing children will move their legs into a comfortable position as easily as if they were forward facing.

How to tell when an older child has outgrown their high back booster: 

When your child is getting to the later stages of using their high-back booster, it can be tempting to take them out as soon as they hit 135cm in height – especially if their friends aren’t in boosters any more! However, even if they are the legal 135cm height limit you may find your child doesn’t have a good belt fit without the booster seat. To check your child can safely and legally sit in the car without a booster, we recommend the five-step test below: 

  1. Your child is at least 135cm in height – this is a legal requirement.
  2. They can sit with their back against the vehicle seat back.
  3. Their knees comfortably bend over the edge of the vehicle seat – they don’t need to slouch to achieve this.
  4. The lap belt fits against their pelvis and isn’t down on their thighs or up on their tummy.
  5. The shoulder belt runs diagonally across the shoulder – running near or across the middle of the collar bone. 

If your child passes these five steps, then they can legally and safely travel in the vehicle with no high back booster. 

So, there is no need to race through the seat stages, and the best part about using each stage to the maximum is that you not only get the best protection for your little one, but your money’s worth out of the seat too! 

Author Kat Gemmell

Kat Gemmell joined our car safety team with over a decade of experience supporting parents to choose, fit and use their child car seats safely. She has worked for a national child seat campaign, provided product training for child seat manufacturers, and ran online information websites to support parents in making a truly informed choice.


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