Ratings from the Insurance Institute for Highway Safety take the guesswork out of selecting boosters most likely to provide good lap and shoulder belt fit in a range of vehicles.

Unlike child restraints with built-in harnesses, booster seats rely on vehicle safety belts to restrain children. Boosters are supposed to make adult belts fit children better. Booster seats are for kids who have outgrown their forward-facing restraints.

Proper fit is key

Our ratings identify boosters most likely to provide good lap and shoulder belt fit. Safety belts are designed with adults in mind, not kids, but when a booster seat is doing its job, the vehicle belt will fit a child correctly. That means the lap belt will lie flat across a child's upper thighs, not across the soft abdomen, and the shoulder belt will cross snugly over the middle of a child's shoulder.

The Institute puts the booster seats it tests into 4 categories: