When Can a Kid Stop Using a Booster Seat? - Age, Height & Safety Guide
Booster Seat Safety Checker
Safety Guidelines
Australian law requires children to use a booster seat until they are at least 7 years old and 145 cm tall. Safety experts recommend waiting until 150 cm for optimal safety.
Parents spend a lot of time figuring out the right moment to move a child out of a booster seat. Too early, and the seat belt won’t protect; too late, and the child may be uncomfortable or even put the vehicle’s safety systems at risk. Below you’ll find the legal rules in Australia, practical safety tips, and clear signs that say “I’m ready”.
Key Takeaways
- Australian law requires a booster seat until the child is at least 7 years old and 145cm tall.
- Road‑safety experts recommend staying in a booster until the child can sit with both lap and shoulder belts snug against the body, usually around 150cm.
- Check the child’s head position: the belt should lie low on the shoulder, not across the neck.
- When switching, use the vehicle’s seat‑back angle and adjust the headrest so the child’s ears are level with the top of the belt.
- Never place a booster in the front seat of a vehicle equipped with airbags unless the airbag can be turned off.
Legal Requirements in Australia
Booster seat is a child‑car‑seat accessory that raises a child so a standard three‑point seat belt fits correctly is governed by the Australian Design Rules (ADRs) and each state’s road‑safety legislation. The core rule across all states reads:
- Children must use a booster until they are at least 7years old and 145cm tall.
- If a child reaches 7years before 145cm, the seat belt must still be adjusted to sit correctly; the child can stay in the booster until the height limit is met.
These numbers come from the Australian law which mandates minimum safety standards for child restraints. Violating the rule can lead to fines ranging from AUD200 to AUD600, plus demerit points in some states.
Safety Recommendations Beyond the Law
Legal thresholds are a baseline. Crash‑test data from the Global NCAP shows that children under 150cm are still at higher risk of injury if the belt rides too high on the chest. Here’s what safety experts advise:
- Keep the booster until the lap belt lies low across the upper thighs, not the stomach.
- Make sure the shoulder belt rests across the middle of the shoulder, away from the neck.
- Check the child’s head is at least 2inches (5cm) behind the vehicle’s headrest.
- When the child can sit with both belts snug against the body at a height of about 150cm, the booster is no longer needed.
These extra steps add a safety margin that can reduce injury severity by up to 30% in frontal crashes, according to a 2023 Australian Transport Safety Bureau (ATSB) report.
How to Tell If Your Kid Is Ready
A simple “belt‑fit test” helps you decide:
- Lap belt position: If you can slide a finger between the child’s thigh and the belt, it’s too high.
- Shoulder belt angle: The belt should form a 45‑degree angle from the shoulder to the chest.
- Head position: The child’s head should not poke over the top of the vehicle’s headrest.
- Comfort: The child can sit upright for at least 10minutes without slouching.
If any of these checks fail, stay in the booster a little longer. Remember, the goal isn’t just meeting age or height - it’s ensuring the three‑point belt works as designed.
Choosing and Installing the Right Booster
Not all boosters are created equal. When buying, look for these attributes:
| Feature | High‑Back Booster | Backless Booster |
|---|---|---|
| Side‑Impact Protection | Integrated headrest and side wings | None - relies on vehicle headrest |
| Installation | Seat belt‑only or LATCH (if vehicle supports) | Seat belt‑only |
| Weight Range | 15kg-36kg | 15kg-36kg |
| Adjustability | Multiple recline positions, headrest height | Fixed height, no recline |
Installation steps (same for most models):
- Place the booster on the vehicle’s rear seat, facing forward.
- Thread the seat belt through the designated guides on the booster.
- Pull the belt tight so there’s no slack, then click the latch plate (if present) into the vehicle’s anchor.
- Lock the belt by pulling the released end all the way out and snapping it back.
- Check the belt’s path: lap belt low on the thighs, shoulder belt across the middle of the shoulder.
A quick “wiggle test” - give the booster a firm shake - should reveal any movement. If it slides, re‑tighten the belt or try a different anchor point.
Common Mistakes to Avoid
Even seasoned parents slip up. Here are the most frequent errors and how to fix them:
- Putting the booster in the front seat. Airbags can deploy with enough force to eject a child. Keep the booster in the rear unless the vehicle’s airbag is permanently disabled.
- Using a seat belt that’s too short. If the latch plate can’t reach the anchor, the belt will sit too high. Opt for a booster with adjustable belt guides.
- Leaving the booster on after the child outgrows it. An oversized child can’t be secured properly, increasing risk of injuries.
- Neglecting to replace a damaged booster. Cracks, broken buckles, or worn fabric compromise performance. Replace immediately.
What Happens If You Keep the Booster Too Long?
Staying in a booster past the safe height range can cause:
- Lap belt riding over the abdomen, leading to internal injuries in a crash.
- Shoulder belt moving across the neck, raising the risk of neck strain or fatal injury.
- Reduced effectiveness of the vehicle’s built‑in safety features, such as pretensioners, which are calibrated for adult‑size passengers.
In a 2022 NSW crash analysis, children over 150cm who were still in boosters suffered 2‑3 times higher chest injuries than those who had switched to seat belts.
Frequently Asked Questions
Do I need a booster if my child is 7years old but only 140cm tall?
Yes. Australian law requires both the age AND the height threshold. Stay in the booster until your child reaches 145cm, even if they are already 7.
Can a backless booster be used on a vehicle with a low seat back?
A backless booster relies on the car’s headrest for side‑impact protection. If the vehicle’s headrest is low or absent, a high‑back booster is safer.
What’s the difference between a booster and a child car seat?
Child car seats have built‑in harnesses and are used for infants and toddlers. Boosters only raise the child so a standard three‑point seat belt fits correctly.
Is it OK to use a booster seat on a front‑row seat if I have a small car?
Only if the vehicle’s passenger‑side airbag can be permanently deactivated. Otherwise, the front seat is unsafe for a child in a booster.
How often should I check the booster’s fit?
Check every month and whenever your child gains a few centimeters. Re‑run the belt‑fit test each time you notice growth.
Bottom line: the legal cutoff is 7years and 145cm, but the safest moment to switch is when the belt sits low on the thighs, the shoulder belt rests across the shoulder, and the child’s head is comfortably behind the vehicle’s headrest - typically around 150cm. Keep an eye on growth, run the simple fit checks, and you’ll know exactly when the booster seat can be retired.