What is a car seat?

A car seat is a detachable seat with a hard shell, used to transport your baby or child in a vehicle. It’s your most important buy and should be top of your pre-baby shopping-list – you won’t be allowed home from hospital without one.


Most car seats use a harness to hold your baby in place and are secured into the car using the car seat belts. However, there are alternative fastening systems such as ISOFIX and in-car base units that fix the seat directly onto the interior of the car.

Maxi-Cosi Pebble car seat

How much does your baby weigh?

The range of car seats on the market is mindboggling and the system for classifying each car seat can feel equally as confusing at first. The key thing you need to know is that your choice of car seat is based on your baby’s weight and height, and not age. Car seats are divided in Groups, and each Group covers a specific weight range:

  • Group 0: 0-10kg, which is from birth to around 6 months
  • Group 0+: 0-13kg, which is from birth to around 15 months
  • Group 1: 9kg-18kg, which is roughly from 9 months to 4 years
  • Group 2/3: 15kg-36kg, which is roughly around 4 to 12 years
Kiddy Comfort Pro car seat- Group 1/2/3

Do you want it to last for years?

Buying a new car seat for every stage would be an (very) expensive business, so thankfully there are combination, or multi-group, car seats on the market. These car seats cover a range (but not all) of the Groups.

The main multi-group car seats are:

More like this
  • Group 0+/1: 0-18kg, from birth to around 4 years
  • Group 1/2/3: 9kg-36kg, from around 9 months to 12 years
  • Group 2/3: 15kg-36kg, which is roughly around 4 to 12 years

While these are pricier than single-group, or single-stage, car seats, they’re an investment and will save you money in the long run.

Other things to bear in mind if you do opt for a multi-group seat are weight and portability. Most Group 0+ seats weigh around 3.5kg, can be teamed with a buggy to create a travel system and are easy to carry with a sleeping baby on board. However a Group 0+/1 car seat can weigh a lot more and won’t be easy to move out of the car to the home, nor will it be compatible with a buggy to create a travel system. Also, what you gain in a longer lifespan and flexibility, you may lose in fit - a seat catering for such a range of weights and ages may not be as snug as a single Group car seat.

Mamas & Papas Primo Viaggio IP car seat

Do you need a rear facing car seat?

In the UK the current law recommends your baby travels in rear facing car seats (those that face to the boot of the car) from birth to 9kg or around 9 months.

The new i-Size law, due to take over the current law in 2018 requires babies to sit rear-facing until at least 15 months old. A rear facing car seat provides greater protection for your baby's head, neck and spine than a forward facing seat.

You should only move your baby into a forward facing seat when they’ve exceeded the maximum weight for their baby car seat, or the top of their head is higher than the top of the car seat.

But there’s no rush to move onto a forward facing seat. Recent research on car seats (2009) suggests that rear facing seats are preferable for children up to 18kg (around 4 years) because they reduce the problem of the head being flung forward on impact.

There’s some evidence that long periods in upright car seats may restrict breathing in newborn babies. So, it’s useful to know there are also lie-flat car seats that are suitable from birth to around 6 months. These are in the Group 0 category and lie across the back seat of the car and are secured by the seat belts.

Mamas & Papas Sola buggy with Mamas & Papas Cybex Aton car seat

Do you need it to work with a buggy?

A travel system combines a buggy with a car seat. The car seat clicks, or slots, onto the buggy or its chassis, making it easy to move your baby from car to buggy. Travel systems are a doddle to use and cut out the stress of disturbing your baby. But the size and weight of most car seats means that only a Group 0 or Group 0+ car seat can be paired with a buggy to make a travel system.

If this idea appeals to you, check out our buyer’s guide to travel systems.

Jane Montecarlo Plus car seat

Do you need ISOFIX?

ISOFIX stands for International Standards Organisation FIX. It’s a standard system for fixing child car seats into cars. The system sees the base of the car seat hooked onto two small metal bars, or anchor points, in your car. These are usually positioned where the back seat meets the seat cushion.

ISOFIX is designed to make fitting child seats quick and simple and to avoid the problem of incorrect fitting. The AA estimated, in 2009, that two thirds of car seats were fitted incorrectly.


  • ISOFIX avoids the problems of securing a car seat with a seat belt (seat belts can differ wildly in length)
  • It creates a rigid link between the seat and the car and is more secure than the seatbelt method, so your child will be better protected in a crash


  • Since 2006, all new cars have been required by law to have two ISOFIX fittings (Semi-Universal). However, a 3-point (Universal) system also exists. Check with your car handbook before buying a car seat with ISOFIX!

We’ve got more in-depth info on ISOFIX for you.

Maxi-Cosi Pearl with Maxi-Cosi FamilyFix base car seat

Do you need an in-car base?

An alternative to ISOFIX, or using only the seat belt to secure your car seat, is to slot the seat onto a rigid in-car base. Base units sit on top of the car seat cushion and are secured either using the ISOFIX points or a regular 3-point seat belt.

Using an in-car base raises the height of the car seat, can provide extra legroom and makes correct installation simple. Some base units have light or sound indicators that confirm correct fitting. Simply slotting the seat in and out makes it easy to use with a travel system but be aware that if you choose this option, you could double the price you pay.

Maxi-Cosi Rodi XR car seat

What’s the latest safety advice on car seats?

In the UK there’s clear advice for using and installing car seats, which was revised in 2006.

All children under the age of 12, or under 135cm in height, must use a car seat appropriate to their weight, height and age when travelling in a car.

According to RoSPA (The Royal Society for the Prevention of Accidents), forward facing car seats can be used in the front of the car as long as they’re appropriate for your child’s weight, height and age. But the law says rear facing infant car seats (Group 0 and Group 0+) must not be used in the front seat of the car when the air bag is switched on.

There are three exceptions where a car seat doesn’t have to be used, but in each case your child must use the adult seat belt and must travel in the rear of the car:

  1. In a licensed taxi or private hire vehicle
  2. If travelling a short distance in an emergency
  3. If there are three children in the rear and two car seats that prevent a third being fitted

Head to our round-up of the latest car seat laws for more details.

Another thing to be aware of is second-hand car seats - avoid them and buy a new one. You don't know for certain if it has/hasn't been in an accident, and all the necessary instruction may not be with it.

Recaro Young Profi Plus car seat

Where do you start?

Choosing a car seat can be confusing – there’s a huge amount of technical speak to get your head around before you even get started. But our in-depth reviews of car seats to use from birth, from 9kg/9 months and from 15kg/4 years should make choosing the right model easy.

We’ve also complied round-ups of 10 of the best suggestions to save time: