Car seat: how to choose by height, not by age

i-Size and the old group system

The old system divided car seats into groups 0 to III by the child's weight. The newer i-Size standard is based on height and is more accurate: two children of the same weight can differ in height, and the belt runs over the shoulder, not over the weight.

i-Size seats are also tested for side impact and require rear-facing travel until at least fifteen months. If you are choosing today, it is the simpler and safer reference point.

When to turn the seat forward-facing

The longer a child travels rear-facing, the lower the risk of neck injury in sudden braking. The minimum requirement is fifteen months, but it is recommended to keep it until at least four years, as long as the seat allows.

Bent legs resting against the seat are not a problem and not a reason to turn the seat earlier. Children find this position comfortable, and leg injuries in such seats are rare.

Isofix and belt installation

Isofix attachment to the car body is more reliable simply because it is harder to install incorrectly. Most mistakes come from installation, not from the design of the seat itself.

A seat with Isofix is almost always completed by a support leg or a top tether — both designed to stop the seat rotating forward. A skipped top tether is the most common silent mistake.

• Check whether your car has Isofix anchor points
• A support leg is not suitable if there is a storage box under the floor mat
• The seat should not move more than a few centimetres at the base

What not to do

A used seat from a stranger is a risk you cannot see: after an accident a seat is no longer fit for use, even if it looks intact. The same applies to seats more than ten years old.

Thick jackets under the harness are the second common mistake. In a crash the padding compresses, the harness becomes loose, and the whole system works differently from how it was tested — so it is better to take the jacket off and lay it on top.