The best car seats for 3-year-olds

In need of a new car seat for your three-year-old? These are the best to buy.

best-car-seat-for-3-year-old

by Eleanor Weaver |

At the age of three, your little one is likely to have outgrown their baby car seat and now needs a car seat that’s suitable for their weight and height, and safe and secure enough to harness a wriggling three-year-old!

In the UK, it’s a legal requirement for children to use a car seat until the age of 12 or 135cm in height, so a car seat for your three-year-old is a must.

But which type of car seat do they need? And which are the best? We’ve shared everything you need to know about the best car seat for a three-year-old.

What car seat does a 3-year-old need?

Car seats for children are determined by their weight, rather than their age, under ECE R44 regulations, and so by using this measurement, you’ll be able to find the best ‘stage group’ for your little one.

All of the below stage groups would be suitable for a three-year-old:

Group 0+/1 car seats: Suitable from birth to 18kg, approx. four-years-old.

Group 1 car seats: Suitable for children 9-18kg, approx. nine months to four years old.

Group 0+/1/2 car seats: Suitable from birth to 25kg, approx. six-years-old.

Group 1/2/3 car seats: Suitable for children 9-36kg, approx. nine months to 12 years.

Group 2/3 car seats: Suitable for children 15-36kg, approx. three to 12-years-old.

3-year-old-in-back-of-car

Which car seat should I choose?

If you’re buying a new car seat for a growing three-year-old, we would recommend choosing stage Group 1/2/3 and up. The lower group stages will only be able to be used for a limited amount of time at this age before you need to buy a new car seat. So you wouldn’t be getting the best value for money.

Group 1/2/3 are classed as multi-stage car seats, they’re designed to carry your child from birth to the booster-seat stage, adapting to each stage with the necessary safety features. They are initially more expensive compared to other car seats on the market, but they can be used until your little one is too old – talk about futureproofing! These car seats come with padding, and a five-point safety harness and most of these seats will fit children up to 18 or 25kg.

If your child is already over 15kg, we would recommend choosing a Group 2/3 car seat instead. This seat will lift your child up to use the vehicle seat belt and comes with a high back and side padding for safety and impact protection.

The exception to the weight-based rule lies with i-Size car seats. Using a height-based system instead and expected to be adopted across new car seats in the future, i-Size was introduced in 2013 and under safety regulation - ECE R129, uses rigorous testing through state-of-the-art Q dummies impact trials. Using height as a measurement instead, it takes the guesswork out of choosing the right fit for your child and provides better protection from side impacts. These car seats are also highly recommended.

Can a 3-year-old sit in a booster seat?

This completely depends on your child’s weight and height.


Based on new safety regulations launched in 2017, Group 3 car seats i.e. new booster seats on the market, are limited to children who are taller than 125cm, weighing more than 22kg. The average height and weight of a three-year-old in the UK fall below these requirements, so it’s likely they would not be able to use a booster seat.


It’s recommended that you should keep your child in the lowest stage group possible as these provide the best safety features.

What is ISOFIX?

We’ve mentioned ISOFIX a few times, but if you’re not in the know, you’ll be wondering what it is. ISOFIX compatible car seats have two arms that lock onto small metal bars located in the seat of your vehicle to anchor the car seat into place. Great for seamless installation with no seat belt threading necessary, they also come accompanied with install indicators, so you can be sure it’s correctly connected.

Most new cars since 2013 have a pair of ISOFIX anchor points but it’s something worth checking if this is the case with your own car if you want to make the most of it.

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