How to fit an infant car seat, step by step

This is general information from public sources, not medical advice. For anything about your child's health or development, speak to your doctor or health visitor.

Your seat's own manual comes first, every time. Seats differ, and the labels on the side of the seat show how yours fits. These are the general steps from RoSPA's child car seat site. It's worth practising before the birth, as the NHS suggests, so the first go isn't in a hospital car park.

Lost the manual? RoSPA says many makers publish theirs online.

Choose the spot

RoSPA says the rear of the car is safer than the front. Before you fit anything, think through these points:

Front passenger seat. RoSPA and the NHS both say a rear-facing seat there with an active airbag is dangerous and illegal. GOV.UK says to deactivate any front airbags before fitting one there. Even then, RoSPA says the rear is better.
Behind the passenger. You can usually get your baby in and out from the pavement side, which the NHS recommends.
Middle rear seat. RoSPA calls this the safest place if it has a three-point belt, unless the seat's instructions say another seat is better. An Isofix seat can only go there if there are Isofix points.

Fit it with the seat belt

The Babymore Coco i-Size is one seat that fits this way, and Babymore says it belts into any car without a base. Most infant carriers work on the same broad lines.

Put the seat on the car seat, facing the rear. It should rest squarely.
Run the belt through all the correct guides. RoSPA says these are green on i-Size seats and blue on rear-facing R44 seats.
Push your weight into the seat as you tighten the belt. RoSPA says there should be no slack.
Close any lock-off device if your seat has one.
Check the seat rests firmly, with hardly any movement forwards or sideways.
Check the buckle of the car's belt isn't resting on the child seat frame. RoSPA calls this "buckle crunch", and says the buckle could spring open in a crash.

If the belt won't reach, RoSPA says some seats have an alternative route. Never modify the seat or the belt to make it fit.

Fit it with an Isofix base

Check first that the base is approved for your car. RoSPA says Isofix seats won't fit every car that has Isofix points, and many makers publish a list. For the Coco, the Isofix route is Through optional Coco Isofix base.

Find the Isofix points, using your handbook and the labels on the rear seats. They sit in the joint between the seat back and cushion.
Push the base's two connectors into the slots. On many bases you'll hear a click, or see an indicator turn from red to green.
Set the support leg so it braces against the floor. Some turn green when they're right.
Keep the leg away from any underfloor storage lid. RoSPA says that could collapse in an impact.
If your seat uses a top tether instead, clip it only to the car's tether point, never to a head restraint or luggage hook.
Click the seat onto the base, as your manual shows.

Check the harness each journey

Clothing changes how snugly it fits, so RoSPA suggests checking every journey.

The top of the harness sits about 2cm below the shoulder on a rear-facing seat.
Only one or two fingers fit between your baby's chest and the harness.
The harness buckle doesn't rest over your baby's tummy.
The harness isn't twisted.
No thick coats or snowsuits. RoSPA says a thick jacket or body suit stops the harness fitting close to your baby. The Lullaby Trust advises taking off hats and outdoor clothes once your baby is in the car, to avoid overheating.

Babies do slump sometimes. The Lullaby Trust says to stop if yours slumps forward, take them out and reposition them before driving on.

When you get there

The NHS says it's OK for your baby to fall asleep in a car seat while travelling, but to take them out as soon as you arrive. The Lullaby Trust says to move them to a firm, flat surface. Home sleep stays the same: on the back, in a clear cot, in the same room as you for at least the first 6 months. Questions about a baby born early, or about a health condition, are ones for your doctor or health visitor.

Getting a second pair of eyes

RoSPA suggests getting someone to check the fit if you're unsure, and that's a sensible thing to want. The NHS mentions safety days where experts demonstrate fitting, often in supermarket car parks, and some retailers have trained staff.

Still picking a seat? Try choosing a first car seat, or read what i-Size and R129 mean if the labels are confusing you.