I found it hard to get information on this a few years ago also. My kid was too big to fit in a car seat, but information I found said they are meant to be in them until they’re 8.

Kids can start wearing a regular seatbelt when:

They can easily rest their back against the seat of the car and bend their knees over the edge of the seat with their feet touching the floor.
The lap belt fits comfortably across the upper thighs and hips (not the stomach).
The shoulder strap goes across the chest and shoulder, never beneath a child’s arm, behind their back, or across their neck.
They can sit safely for the entire ride without slouching or leaning.

Usually, this happens when kids are between 8 and 12 years old and around 4 feet 9 inches (about 150 centimeters) tall.

Continue to use a booster seat if your child cannot sit properly or wear the seatbelt correctly.

You can always check with Kidsafe who will be able to fit her properly anyway too.

yeah you could just google it. would be info everywhere. it does go by height if height is acheived before age.

Depending on your state, check our your road authority website (Vic Roads etc). They should have guidelines.

It think it differs fromstate to state. My son is supper short for his age while he has friends that are tall and heavy enough to be out of it at 7 years old he is not. He will be at least nine or ten till he is out of it.

Check out the child safety organisation in your state. I had always thought it was age only.