Choosing a child car seat Car seat weight groups
There are hundreds of child car seats, carrycots and booster seats on the market.
And, as our child car seats crash test video below shows, there are major differences in the protection offered by the best and worst child car seats.
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So how do you know which type of child car seat to choose?
This guide is the ideal starting point. It will help you work out which sort of child car seat your child needs and explain the differences between major types of child car seat.
Then, once you know which sort of child car seat you're looking for, head over to our reviews of child car seats to see the best – and worst – performers in our rigorous tests.
Child car seats: weight groups
When buying a child car seat, the first thing to remember is that your child’s weight is a more important factor than his or her age.
There are five main weight groups for child car seats, and you can use this table to work out which one you'll need to go for.
| Weight categories | ||
|---|---|---|
| Seat group | Weight range | Approximate age range |
| Group 0 | 0-10kg (0-22lb) | From birth to about 11 months (boys) or 14 months (girls) |
| Group 0+ | 0-13kg (0-29lb) | From birth to about 15 months |
| Group 1 | 9-18kg (20-40lb) | About 9 months to 4½ years |
| Group 2 | 15-25kg (33lb - 3st 13lb) | About 3 years to 7 years |
| Group 3 | 22-36kg (3st 7lb - 5st 9lb) | About 6 years to 12 years |
It's safest to buy specific child car seats to suit your child's weight as they grow, rather than one that covers the whole weight range.
Try to keep your child in the lower-group child car seat for as long as you can, but make sure you don't leave it until your child is over the car seat's weight limit before changing.
This means you should use a Group 0+ baby car seat up to at least 10kg, then consider changing to a Group 1 child car seat, which your child will use until they are at least 15kg.
At 15kg (about 3-4 years), think about changing to a Group 2/3 seat, which will suit the child all the way up to age 12, when they should use the adult seat belt.
Our child car seats review shows you how Britax child car seats, Maxi Cosi child car seats and Graco child car seats performed in our rigorous tests.
Child car seats and height
Few children get too tall for a seat in their weight range
In most cases, the child will reach the weight limit of a child car seat before becoming too tall for it.
However, your child will have outgrown the child car seat if his or her eyes are level with the top of the seat.
If they're below the thresholds suggested above, seek advice from a qualified child car seat expert (contact your local authority's road safety office to find out who this is in your area).
In extreme cases they may advise you to seek advice from a doctor or paediatrician.
Protecting premature babies
Newborns shouldn't be made to travel much
We regularly receive queries about child car seats for pre-term babies. We asked Britax technical director Farid Bendjellal about this.
He told us: 'For pre-term and newborn babies, lying flat is ideal for comfort and to reduce the chances of apnoea (respiratory problems).
'But for crash protection, near-vertical is ideal – however, this presents a risk of apnoea. Hence a compromise of around 45 degrees is usually chosen for Group 0+ child car seats.'
Consult your doctor before transporting a pre-term baby by car.
For more information on choosing a child car seat, visit the Royal Society for the Prevention of Accidents (Rospa) website.
For expert advice on making the right product choices for you and your child, read Which? Essential Guide: Baby and Toddler Essentials.