How do I fit a child car seat correctly?

Research repeatedly finds that a large proportion of child seats in use are fitted or used incorrectly. Almost all of those errors are in three places: the seat is loose, the harness is slack, or the seat does not suit the car.

Safety

What you'll need

• The child seat and its instruction manual
• The car handbook
• A retailer fitting check (optional)

Step by step

1. Check the seat suits the child, by height or weight.Newer i-Size seats are chosen by height and require rearward-facing until at least fifteen months. Older weight-based seats are chosen by the child's weight. Read the label on the seat rather than guessing.
2. Check the seat is compatible with your car.Manufacturers publish vehicle compatibility lists. Not every seat fits every car, and a seat that will not sit flat or cannot be tightened is not safe in that car regardless of its rating.
3. Use the rear seat wherever possible.It is the safest place for a child in almost every car. If a front seat must be used, a rearward-facing seat requires the passenger airbag to be switched off, confirmed off, and the seat slid fully back.
4. Read the seat's own instructions properly.Every model differs in belt routing, ISOFIX engagement and support leg use. The instructions are the authority; general advice is not.
5. Use ISOFIX where the car and seat both have it.The connectors click onto anchor points built into the car and remove most of the ways a belt fitting can go wrong. Indicators on the seat should show green on both sides.
6. Fit the top tether or support leg if the seat has one.Both exist to stop the seat rotating forwards. A support leg must rest firmly on the floor, not on a storage compartment lid, and a top tether must be anchored to the proper point, not a luggage hook.
7. For a belted fit, follow the marked belt path exactly.The routes are colour coded on the seat: usually blue for rearward-facing and red for forward-facing. Put your weight into the seat as you pull the belt tight.
8. Test the movement at the belt path.Grip the seat at the point where the belt or ISOFIX passes through and pull side to side and forwards. Movement of more than about an inch means it is not tight enough.
9. Set the harness height correctly.Rearward-facing: harness slots at or just below the child's shoulders. Forward-facing: at or just above. The wrong slot lets the child move too far in an impact.
10. Tighten the harness and check with a pinch.Straps flat and untwisted, chest clip or buckle in the right place, and you should not be able to pinch a horizontal fold of webbing at the collarbone.
11. Take bulky coats off before strapping in.A thick coat compresses in a crash and leaves the harness dangerously slack. Strap the child in, then put the coat on backwards over the top or use a blanket.
12. Have the fit checked and re-check it regularly.Many retailers check fitting free. Re-check tightness every few weeks — seats work loose, and children grow out of harness settings faster than expected.

Tips

• Photograph the correct installation once it is right. It makes refitting after a clean, or in another car, much quicker.
• Never buy a second-hand seat unless you know its full history. An unseen crash can compromise a seat with no visible damage.
• Keep the instruction manual in the car. It is the only document that describes your exact seat.

Common mistakes

• Leaving the harness slack — A harness that allows a horizontal fold to be pinched at the collarbone lets the child move significantly in an impact before being restrained. It is the most common error found in surveys.
• Turning a child forward-facing as early as the law allows — Rearward-facing spreads the force of a frontal impact across the whole back, head and neck. Safety bodies consistently advise staying rearward-facing for as long as the seat allows, not for the minimum period.

If it doesn't work

Questions people ask