Proper Booster Fit

(Last Updated On: April 6, 2019)

Caregivers always worry if their child is in their harnessed car seat correctly. Is the harness at the right height? Properly tightened? Chest clip on the chest? Despite all of those concerns with harnessed car seats, caregivers don’t put the same amount of thought into their child’s booster seat. Just load the child into the booster seat, buckle, and go. So many times, we see booster seats being used incorrectly so they don’t provide the proper protection.

The Insurance Institute for Highway Safety (IIHS) does a booster evaluation every year of Best Bets, Good Bets, Not Recommended, and those that need to Check Fit before use. Thankfully most seats are on the Best Bet list, which makes it easier on care givers. This doesn’t mean all seats will fit all vehicles and all children; booster seats still need to be adjusted to fit the rider.

Poor seat belt fit using Alpha Omega in booster mode proper booster fit

Poor vehicle seat belt fit using Alpha Omega in booster mode

Here is an example of a now mostly-retired car seat that was notorious for its poor booster seat fit. Even though the child using the seat meets the requirements and is using it properly, it would not give proper protection in a crash. You can see the shoulder belt does not contact his shoulder, the lap belt is high on his abdomen and not touching his thighs, his bum is back, but even though he met the minimum requirements to use the seat, at 4 years old there is no way he would maintain this position the entire length of the trip. The belt fit is bad enough I would never recommend this seat be used as a booster.

When to Move to a Booster Seat

The first question to ask is when a child should move from their harnessed car seat into a booster seat? Once a child is at least 5 years old, meets the minimum height and weight requirements for the booster seat, and can sit properly in the seat 100% of the time, a booster seat is an appropriate restraint.

Our Harness or Booster article explains more.

When to Move from a Booster Seat

How long does a child need to use a booster seat? Longer than you think!

Children need booster seats until they can pass the Five Step Test. That’s when they’re around 10-12 years old, are at least 4 feet 9 inches tall, and are able to fit properly in an adult seat belt. Boosters are for Very Big Kids will go over the requirements to move out of a booster in more detail, as will Booster Seat Science.

Proper Booster Fit Guidelines

Proper booster fit has the shoulder belt firmly across the middle of the child's shoulder

Proper booster fit has the shoulder belt firmly across the middle of the child’s shoulder

1.  The shoulder belt should lie firmly in the middle of the child’s shoulder with shoulder belt guide just above the shoulder. The shoulder portion of the vehicle seat belt should be flush against the child’s body. A shoulder belt that doesn’t touch the person can’t properly restrain them.

For proper booster fit, backless boosters require head support to the top of the child's ears at all times

For proper booster fit, backless boosters require head support to the top of the child’s ears at all times

2. If the child is riding in a backless booster, or if the high back booster requires it, be sure there is head support from a vehicle head restraint behind the child’s head to at least the tops of the child’s ears.

Aidia Explorer backless mode with shoulder belt adjuster

Aidia Explorer backless mode with shoulder belt adjuster

Many backless booster seats come equipped with a shoulder belt adjuster clip. This acts as the shoulder belt guide to ensure the shoulder belt is flush with and appropriately positioned above the shoulder.  The attachment strap often will be attached from behind meaning the shoulder belt will then be between the child and the vehicle seat. Few seats require their use, so be sure to read your manual to see if it’s needed and how it should be used.

A proper fitting lap belt is low on the lap and off the child's abdomen

A proper fitting lap belt is low on the lap and off the child’s abdomen

3.  The lap portion of the vehicle seat belt is low on the child’s thighs, off the abdomen, and pulled tight.

For proper booster fit, a child's bum needs to remain all the way back when seated properly in a booster

For proper booster fit, a child’s bum needs to remain all the way back when seated properly in a booster

4.  The child’s rear end is all the way back in the booster seat.  The depth of booster can help with this. For example, taller kids may need deeper boosters while shorter children may have a better fit with a taller booster seat.

If the child cannot remain seated properly in their booster at all times, a harnessed seat will continue to be needed

If the child cannot remain seated properly in their booster at all times, she will need to continue riding in a harnessed seat

5.  The child can maintain this position 100% of the time without moving out of position during the ride. If this cannot be accomplished, then the child should ride in a harnessed car seat until they’re ready to sit properly for the entire ride.

Boosters do a great job at protecting children in a crash. The key is to make sure your child is mature enough to use a booster, meets the criteria to use the booster, you’re using the booster correctly, and the booster fits your vehicle and child correctly.