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What is a booster seat?

Child in booster seat

A booster seat is a car seat without a harness. It raises a child up so the lap and shoulder belt fit right. Children use a booster seat when they are too big for a car seat but not big enough for an adult seat belt. A seat belt that doesn’t fit right won’t protect your child in a crash.

When will my child be ready for a booster seat?

Keep your child in a forward-facing car seat with a 5-point harness until they reach the top height or upper weight limit allowed for that car seat (check the manufacturer’s instructions). Once they outgrow their forward-facing car seat, they can ride in a booster seat. Your child should be at least 40 pounds before they use a booster seat.

In Washington state, it is the law for children to ride in a booster seat until age 8, or until they are 4 feet, 9 inches tall (57 inches). Children under age 13 should ride in the back seat when possible.

Can I use a booster seat with a lap-only belt?

No. Booster seats must be used with a lap and shoulder belt. Never use one with just a lap-only belt.

  • If the center seating position of your back seat has a lap-only belt, place the booster seat in an outboard seat where a lap and shoulder belt must be used with the booster seat.
  • If you do not have a usable lap and shoulder belt in the back, you can use the booster in the front seat with the lap and shoulder belt. Push the front seat back as far as you can. If your car has an air bag, turn it off.
  • If you must use a lap-only belt, your child should wear it low and tight across the hips without using a booster seat.

What kinds of booster seats are there?

No-back booster

No-back booster

High-back booster

High-back booster


A no-back booster can be used in cars with headrests in the back seat. If your child’s head does not rest comfortably in the headrest to protect their head and neck, then use a high-back booster seat.


A high-back booster can be used in cars with or without headrests.

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