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Everything you need to know about i-Size car seats

Everything you need to know about i-Size car seats

Car Seats
i-Size is a EU safety regulation for child car seats which was introduced in July 2013. It is a type-approval category of seat within R129 that describes seats that are compatible with i-Size positions in cars.

i-Size is a EU safety regulation for child car seats which was introduced in July 2013. It is a type-approval category of seat within R129 that describes seats that are compatible with i-Size positions in cars. 

There will be some R129 cars seats that are not i-Size, but still have many of the benefits of the new regulation. The new i-Size regulation is designed to keep children rear-facing for longer, provide better side impact protection and make car seats easier to fit correctly.

Here are the key points of the new EU safety regulation for child car seats explaining what i-Size is, why it’s being introduced and how it might affect you.


From weight to height

Some of the car seat weight ranges are encouraging parents to move their children up to the next stage seat too early. Staying rear facing as long as possible is much safer and the low weight limit for forward facing seats was only designed for the very small percentage of children that grew very tall and thin without adding significant weight. The i-Size (R129) regulation means that seats are classified on the size and height of a child rather than his/her weight. Plus, the R129 stipulates that your child should be rearward facing until at least 15 months old.


Up to 85% of car seats are fitted incorrectly so the new i-Size regulations standardise fitting procedures making it much easier for parents.


Rear facing for longer

The most frequently occurring accidents are frontal impacts (because this is the normal direction of travel) so the safest position for babies is rear facing because the back of the seat supports the head and entire body in the event of a collision. When forward facing, the only support for children is the 5-point harness, so much more force is exerted on the neck leading to a higher risk of injury. This is why the new i-Size regulation mandates rear facing use of the car seat until at least 15 months of age.

i-Size requires ISOFIX fitting

All i-Size car seats must fit into the car with ISOFIX and have a support leg or tether strap to prevent any rotation in a collision. The maximum weight which can be placed on the isofix is 33kg. This can be any combination of car seat and child weight. For example, if the car seat weighs 10kg, the maximum child weight using the ISOFIX is 23kg.

Car compatibility

Many seats regulated under R44 won’t fit into all cars but the new i-Size regulation change this. Car seats certified under R129 fit into one of nine envelope sizes. In order to be considered a universal seat (i.e. can fit in every i-Size ready car) they must fit into one of two specific sizes (one rearward and one forward facing). Seats that fit within one of the other seven envelope sizes can be approved under R129 as vehicle.

Regulated side impact protection

Under the older regulations side impact was not tested despite 28% of fatalities occurring from a side collision. i-Size now legally requires car seats to ensure side impact protection. The i-Size regulation will test seats with an intruding door which moves into the internal car space.

Size instead of weight

Each group of seats tested under R44 have to accommodate a certain weight range. With i-Size it is now required to ensure a car seat fits a child’s heights and width and there will be no predetermined groups e.g. 0, 0+,1,2/3. So, for example a car seat which can be used for a child from birth to 2 years must be large enough to accommodate the height and width of children at birth as well as at 2 years. Obviously, there is some variation in how quickly children grow so car seats will have to be made to accommodate the upper height and size at the maximum age range. This will make it much easier for parents to know if a seat is suitable for their child and how long it will last!


Does it mean R44 seats aren’t safe?

Car Seats legislated under R44 still meet all the legal requirements and can be used without any issues. It is not necessary to throw away your current seat for a new model. While there are some i-Size seats on the market, you don’t have to buy a new car seat, unless you want to. But if you are in the market for a new child car seat you should look for the i-Size logo, as this will slowly phase out seats with older certification in the coming years.

Is R129 better than R44?

R129 (often referred to as i-Size) raises the minimum standard. It improves the compatibility between the child and the car seat and the vehicle seat.

How do I know if my car seat is i-Size?

You can find out easily if a car seat has this approval by looking for the label on the seat.

Am I breaking the law if I don’t have a R129 car seat?

No, you can still legally use an R44 car seat as long as it is suitable for your child and the vehicle in which it will be used.