Child car seat

Has your child outgrown their toddler car seat? Choosing a new seat can feel like an impossible task, especially when there are so many options to choose from and lots of regulations and guidelines to bear in mind.

On top of that, the seat needs to go the distance – from four years old through to primary school and beyond, and then all the way up to age 12. But how do you find a seat that fits all these criteria?

We’ve looked at car seat regulations, spoken to experts from Good Egg Car Safety and Rear-Facing Toddlers, and tested a shortlist of child car seats to make things easier for you.

This buyer's guide will cover

1. What types of child car seats are available?
2. What is a high back booster seat?
3. What is ISOFIX?
4. What is i-Size?
5. What is the difference between R44 and R129?
6. Is a backless booster seat safe?
7. Collision and side impact testing
8. How much should I spend?
9. Can you use secondhand car seats?
10. Other things to consider

Related: Confused about car seats? A car seat expert answers your most frequently asked questions

What types of child car seats are available?

UK law states that all children need to be in a car seat up to the age of 12 or 135cm (whichever comes first). When buying a seat at this stage, ideally you'll want it to last until your child no longer needs one.

There are five types of child car seats available to buy:

  1. Group 1/2/3 (R44/04): This combination car seat can be used from 9kg to 36kg, from approximately nine months old to age 12 (or 135cm).
  2. Group 2 (R44/04): Offering less longevity than other car child car seats, Group 2 high back booster seats are suitable from 15kg to 25kg (or approximately four to six years of age).
  3. Group 2/3 (R44/04): Suitable from approximately four years up to age 12 or 135cm, this seat can be used from 15kg to 36kg.
  4. Group 3 (R44/04): Can be used with children who weigh 22kg to 36kg and are 125cm or taller.
  5. i-Size (R129): Conforming to the R129 regulation, i-Size car seats for this age group can be used from 100cm to 135cm, or from 135cm to 150cm in specific vehicles.

What is a high back booster seat?

A high back booster cushion is a car seat that has sides (usually well-padded) and a headrest.

It will provide routing for the shoulder and lap part of the car's seatbelt, but, depending on the specific seat and the car it's fitted in, it can often be used in combination with ISOFIX fixings as well.

What is ISOFIX?

ISOFIX is a structural system built into the car that has fitting points to attach an ISOFIX car seat.

Seats at this stage are usually able to be fitted using ISOFIX in conjunction with the car's three-point seatbelt, or the seatbelt only. Margaret Bolt, founder of Rear-Facing Toddlers, advises that, if your car has ISOFIX points, you should always get a high back booster that can be connected to them as this will provide more stability than just using a seatbelt alone.

ISOFIX installation also minimises the chances of parents installing the car seat incorrectly. More and more high back booster manufacturers are including ISOFIX installation as standard, so it’s definitely something to look out for when you’re shopping around.

You’ll be able to find out if your car has ISOFIX attachments by looking for tags or labels in the base of the seat or by contacting your manufacturer.

Read more about ISOFIX here.

britax romer car seat

What is i-Size?

i-Size seats meet the new R129 European car seat safety standards that came into force in July 2013, which aim to increase the safety performance of all car seats on the market.

R129 regulations are currently running in parallel with R44/04 so you can buy car seats that adhere to either guidelines. At some point, R44 car seats will be phased out of the shops – but it's unclear exactly when this will happen.

What is the difference between R44 and R129?


  • Classification based on weight
  • Rear and front impact testing
  • Can be fitted using seatbelt or ISOFIX points
  • Seat must be rear-facing until your child weighs 9kg


  • Classification is based on height
  • Rear, front and side-impact testing
  • Seat is attached with ISOFIX points
  • Seat must be rear-facing until your child is older than 15 months

What is a backless booster seat and is it safe?

A backless booster seat is a seat cushion that is routed into the car using the lap part of the seatbelt only.

Legislation around high back booster seats and booster cushions changed in March 2017. An amendment to R44/04 means that new-to-market cushions approved after this date can only be used with children weighing more than 22kg who are taller than 125cm.

If a booster cushion was approved before this amendment, the approval relates to Group 2/3 (15 to 36kg) seats. As such, if the label on the booster cushion has a stated weight of 15kg to 36kg, it is still legal to use.

However, as Jan James, CO of Good Egg Car Safety, points out, this does not mean it is the safest option for a younger child. Booster cushions are unable to provide side impact protection, which a high back booster can, and this is especially necessary for younger children (although it is also important for older children).

Good Egg Car Safety recommends that a child uses a high back booster for as long as possible, even if the backrest is able to be removed, as maximum protection is offered when using the backrest.

A headrest is also essential to keep your child’s head safe in the event of a crash and it will also come in handy for those quick power naps in between swimming and football or on the long drive to the grandparents' house at the weekend.

Some seats even have reclining headrests to ensure your child’s head doesn’t loll forward when they nod off, keeping their head safely within the padding of the headrest.

Collision and side impact testing

Car seat laws require all car seats to comply with R44/03 or R44/04. You’ll see an ‘E’ label with a capital E in a circle on the seat.

This means that every seat is subject to frontal collision testing at a speed of 50km/h. Only rear-facing seats undergo rear impact collision testing at 30km/h.

Seats complying with R44/04 must also go through a rollover test. These tests are carried out using dummies that represent the weight category of the child approved for a particular seat group.

In addition to these tests, R129 (i-Size) car seats are also undergo side impact testing. Side impact protection absorbs the force of the impact in the event of a crash to protect your child's spine, neck and muscles. Some car seats also have a stabiliser that touches the door closest to the car seat, which helps to absorb the force of the impact as well.

Always look at a seat’s overall crash test rating before you buy.

How much should I spend on a child car seat?

Prices vary considerably and it's worth looking into exactly what the higher-priced seats offer before splashing out. The most expensive seats aren’t necessarily the best.

Safety is the most important thing and seats must conform to R44 or R129 regulations. Bigger brands often conduct their own safety testing too.

So of you’re on a tight budget, do keep safety in mind as your first priority and make sure you always check independent reviews before buying.

Can you use secondhand car seats?

A car seat's main job is to protect your child and, for that purpose, it tends to be a single-use item. You can use a car seat until you have an accident, at which point it must be thrown away and replaced.

While secondhand seats aren't necessarily unsafe, if you buy a seat from someone you don't know you have no real way of knowing the seat's history. This may not be the case if it's been passed down from a relative or a friend, but even if the seat looks fine it could still have suffered invisible damage that has made it weak or unsafe.

As such, experts from Good Egg Car Safety recommend never buying a secondhand seat.

Depends on your car and how wide the seats are as to which seat will fit best in the middle. A good idea to find out whether they will all fit across the backseat is to take all the seats with you when you go to buy your new one.

Other things to consider when buying a child's car seat

1. Comfort

Your child will be spending a lot of time in their car seat, so it’s important to make sure it’s really comfortable.

Does the seat have enough room for them? Is their head and neck comfortable, secure and supported? Even big kids need a nap on a long journey so, if you travel long distances, will the seat be comfortable enough to sleep in?

2. Longevity

One of the most tricky things to get right at this stage is choosing a car seat that will last. What appeals to your four-year-old now will still need to appeal to your 11-year-old.

If you think your child will be concerned that a high back seat is ‘babyish’, think really carefully about choosing a seat that has a simple, sleek design – one that will fit in seamlessly with your car's interior and that can be differentiated from the seat they had when they were younger.

Also make sure that your child will be able to get in and out of the seat and do up the belt themselves – they won’t want you strapping them in!

3. Size

Depending on the size of your car and how many children of car seat age you have, it may be tricky to fit three car seats across the back seat.

Make sure you not only look at whether the car seat will actually fit your car (some won't!), but also the dimensions of the car seat itself to make sure it won't hog the entirety of your back seat.

4. How easy is the seat to clean?

It’s got to last you a while, and it’s going to take a hammering on all those school runs and longer journeys too, so make sure you choose a seat with easily removable and washable covers. You'll thank us later.

Useful resources

About Mumsnet Reviews

All Mumsnet product reviews are written by real parents after weeks of research and testing – this includes recommendations from the Mumsnet forums. We work hard to provide honest and independent advice you can trust. Sometimes, we earn revenue through affiliate (click-to-buy) links in our articles. However, we never allow this to influence our coverage. Read our how we test page to find out more.

All prices correct at time of publication