Which? uses cookies to improve our sites and by continuing you agree to our cookies policy

Booster seats

Booster seats and multiple group child car seats

By Anna Studman

Article 1 of 2

Find out whether a combined or multiple group child car seat is a good idea, and why we don't recommend backless booster seats.

Put us to the test

Our Test Labs compare features and prices on a range of products. Try Which? to unlock our reviews. You'll instantly be able to compare our test scores, so you can make sure you don't get stuck with a Don't Buy.

Are combined group child car seats a good idea?

All child car seats are categorised according to either a child's weight or height. Some seats span more than one weight group, and these seem good value because they'll last your child for longer. But there's a big difference between a 9kg baby and a 36kg child, so can these seats really achieve the same protection as single-group seats?

Generally we think you're better off buying a dedicated Group 0+ and then Group 1 seat for your child. A combined Group 2/3 seat is fine but we don't recommend backless booster seats (group 3).

Group 0+/1/2 child car seats

These are designed to last a child from birth to 25kg (approximately six years old).

Children change too much from birth to 25kg  for one seat shell to adequately provide the protection they need at each stage.

We've tested some very poor Group 0/1/2 child car seats in the past, which fail to position the adult seat belt correctly on the child and could injure their neck and internal organs in a crash.

Group 1/2/3 child car seats

There are many Group 1/2/3 seats available, which can be used from nine months all the way up to 12 years (9-36kg). These allow you to secure your baby in a five-point safety harness, then it converts to a high-backed booster seat when your child is older and bigger.

Generally, car seats designed to span more than two groups do not always provide good levels of protection in all weight groups, but there are some exceptions.

Find out which car seats scored top in our tests in our child car seat reviews

Why we don't recommend backless booster seats and cushions

Some Group 2/3 car seats convert to a group 3 seat, which is just a booster cushion. These raise the child's body to a height suitable for use with the adult seatbelt, but booster cushions are not as safe as a high-backed booster seat with a full-length back and 'wings', which provide extra protection for the head and chest in a side-impact crash.

Watch the video above to see the differences - with and without the back fitted.

A booster cushion satisfies the legal requirement for children up to 1.35m (approximately 4ft 6in) and they're cheap (about £6-£30), but we don't recommend them, especially for younger children, high-backed child car seats are safer, so it's worth paying a bit more for extra protection.

New rules for booster seats

From March 1 2017 the approval rules for booster seats have changed. This means any newly-approved backless booster seat on sale will be limited for use only with children taller than 125cm and weighing more than 22kg. 

You will still see other backless booster seats that don't need new approval on sale and approved for use by children of between 15kg and 36kg.

Both seats are legal to use as long as you are following what is say on the label. So always make sure you check the label.

If you already own a backless booster seat you can still use it, although our car seat experts and many other car seat experts believe that backless booster seats are not the best way to transport children, and recommend using a high-backed booster seat.

Please remember, it's illegal not to use the correct child car seat. 

See our top five high-backed booster seats.

Also look at the seats we recommend you avoid – our child car seat Don't Buys