MAKING sure your baby is safe while travelling is a priority for all parents and a car seat is one way to ensure that happens.
Children must use a child car seat until they are 12 years old or 135cm (4ft 5in) tall, or whichever comes first, according to reports by the BBC.
Under current laws, both families and manufacturers can no longer introduce new models of backless booster seats for children shorter than 125cm or weighing less than 22kg.
But knowing when to move into a new car seat can be tricky, however, experts at Which? have revealed the six easy ways to know when your baby needs a bigger booster.
How long is your baby?
R129 i-Size regulations mean that car seat categories are based on different height measurements.


To measure your baby, lie them down and measure from the crown of their head to their toes, keeping their legs as straight as you can.
It is important to keep your baby in their seat until they reach the maximum height limit to make sure they receive the most protection at the event of a crash.
How heavy is your baby?
The older, but still legal R44, are separated into categories dependent on weight, giving each weight a ‘group’, these include:
- Group 0 – Newborn to 10kg (around 6 months)
- Group 0+ – Newborn to 13kg (around 12 to 15 months old)
- Group 0+/1 – Newborn to 18kg (around four years old)
- Group 0+/1/2 – Newborn to 25kg (around six or seven years old)
- Group 0+/1/2/3 – Newborn to 36kg (around 12 years old)
- Group 1 – 9kg to 18kg (nine months to four years old)
- Group 1/2 – 9kg to 25kg (nine months to six or seven years old)
- Group 1/2/3 – 9kg to 36kg (nine months to 12 years old)
- Group 2/3 – 15kg to 36kg (four years to 12 years old)
- Group 3 – 22kg to 36kg (125cm or around five or six to 12 years old)
Do a head check (literally)
The quickest and easiest way to check whether a child has outgrown a car seat is by taking a look at their head.
If it reaches higher than the head rest it is time for a change as it no longer provides protection to your child’s head.
Strap in
Another simple check to do is checking the position of your child’s car seat straps.
If they are rear-facing (as Which? recommends doing until the age of four) the point where the straps meet the car seat should be at, or just below, the child’s shoulders.


If they are forward facing the straps should be at or just above their shoulders.
You can tell it might be time for the car seat to be moved to a forward facing position if your child is forced to bend their knees or sit cross legged.
How do I fit a car seat?
- Make sure the seat itself is fitted as securely as possible, with no excessive movement.
- You must only use a child car seat if your car’s seat belt has a diagonal strap, unless the seat is either specifically designed for use with a lap seat belt or isfitted using ISOFIX anchor points
- You must also deactivate any front airbags before fitting a rear-facing baby seat in a front seat and not fit a child car seat in side-facing seats.
- And make sure the seat’s buckle is clear of its frame – because otherwise it could snap open if you have an accident.
- With babies, harnesses should be pulled tight, with no more than two fingers’ space under the shoulder straps at the collar bone.
- The harness buckle should be as low as possible, to keep the lap section of the harness across your child’s pelvis, and not resting on his or her stomach.
- Check the harness and chest pads are adjusted according to the instructions.