# How do I know my car seat is fitted correctly? | Clever Mum

> ISOFIX: both indicators green, support leg firm to the floor or top tether tight. Belt-fitted: follow the exact routing diagram, then push your full weight

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#  How do I know my car seat is fitted correctly? 

    
 
Quick answer — How do I know my car seat is fitted correctly? 

 
ISOFIX: both indicators green, support leg firm to the floor or top tether tight. Belt-fitted: follow the exact routing diagram, then push your full weight into the seat while tightening — it shouldn’t move more than an inch at the belt path. Harness at or just below the shoulders, pinch-test tight. Many retailers and some fire services check fits free.

   
## The ISOFIX checklist

* **Both connector indicators green** — half-clicked connectors show red or half-red on every major brand.
* **Support leg firm to the floor**, indicator green, and *not* resting on an underfloor storage lid (check your car's handbook — some need a floor insert).
* **Or top tether tight** to the marked anchor point, not to a luggage hook.
* **Seat checked against the compatibility list** for your exact car — ISOFIX standardises the connection, not the fit.

## The belt-fit checklist

Follow the routing diagram exactly (blue guides for rear-facing, red for forward), then push your full body weight into the seat while pulling the belt tight. Test at the belt path: the seat shouldn't move more than about 2–3cm side to side or forward.

## The harness, every single trip

Height at or just below the shoulders rear-facing (at or just above, forward-facing). Pinch test: with the harness done up, you shouldn't be able to pinch a horizontal fold of strap at the collarbone. Thick coats off before strapping in — compression in a crash turns a snug harness into a loose one.

## Free expert checks

Many nursery retailers, some fire services and local road safety teams run free fitting checks — one appointment catches the errors you can't see yourself. Our [car seat guide](/best/best-car-seats-uk) covers choosing the right R129 seat in the first place.

  
 **Go deeper:**  [Best car seats (i-Size)](/best/best-car-seats-uk/) 

    
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