To know if a car seat’s harness is tight enough, it must pass the pinch test. Adjust the harness, then try to pinch the webbing at the child’s shoulder.
Be aware that slack can be hiding in some additional locations:
- at the child’s hips
- at the child’s torso
If you can grasp any material and pinch the harness vertically between your fingers, it’s too loose. Keep making small tugs on the harness adjuster until your fingers slide right off the webbing.