Convertible car seat height markers were introduced with the 2010 Australian Standard. The 2013 Australian Standard introduced new shoulder height markers for extended rear-facing and extended harnessing.
Convertible car seats can include extended rear-facing (A4) car seats, which let a child travel rear-facing for an extended period — on average, up to approximately 30 months.
📏 How height markers work
Ignore what you think is the right call for keeping your child rear-facing — follow the shoulder height markers on the seat itself. They’re the accurate way to know when to transition.
⬆️ Upper marker
Indicates the maximum shoulder height for that restraint. When your child’s shoulder reaches the top marker, they’re ready for the next type of restraint.
⬇️ Lower marker
Indicates the minimum shoulder height before a child can be turned forward-facing. Below this marker, they should stay rear-facing.
🔤 A2 convertible car seat height markers
Other convertible car seats may be referred to as A2/B car seats — meaning the seat has been tested to at least an average 12-month-old. There’s no fixed standard for exactly where the lower or upper height marker should sit, but minimum standards apply.
For an A2 convertible child restraint, this marker is a minimum of 35cm.
🔤 A4 height markers
The A4 child restraint type was introduced in the 2013 Australian Standard, finally approved on 17 September 2014. An A4 car seat has three shoulder height markers — the lowest marker indicates you can turn your child forward-facing, but you can leave them rear-facing until they reach the middle shoulder height marker.
⚠️ How markers differ between brands
The highest rear-facing shoulder height marker should sit at 39cm. However, some manufacturers don’t reach that — the Maxi Cosi Euro and Maxi Cosi Hera have their second marker at only 37cm.
That 2cm difference means you’d need to turn your child forward-facing at an earlier age than with brands offering a 39cm marker, such as Infa Secure and Britax.
It’s also worth noting that Maxi Cosi needed to recall their original A4 car seats, as they weren’t certified by SAI Global.
📊 Convertible car seat comparison (0–4)
Listed in descending order by tallest rear-facing marker
| Seat | Rear-facing to | Forward-facing to |
|---|---|---|
| Safe n Sound Meridian SICT / Platinum SICT / Platinum SICT Isofix (A4, current) | Not yet published | Not yet published |
| Safe n Sound Meridian SICT / Platinum SICT (pre-2014) | 36–37cm | 43–44cm |
| Safe n Sound Compaq AHR | 36cm | 44cm |
| Infa Secure Kompressor / Neon / Glider / Ascent / Cosi Compact / Trident | 34–36cm | 41.5–43cm |
| Safe n Sound Compaq / Meridian / Haven | 34–35cm | 43cm |
| Hipod Milan | 33cm | 43cm |
| Hipod Cairo | 33cm | 42cm |
| Maxi Cosi Hera | 33cm | 41cm |
| Cargo Hybrid | 32cm | 42cm |
| Mothers Choice Emperor | 32cm | 40cm |
| Babylove Cosmic | 31cm | 41cm |
| Safety 1st Sentinel | 30cm | 38cm |
The current-generation Meridian/Platinum SICT figures weren’t available in our source data — worth updating with current measurements when confirmed.
❓ Frequently asked questions
What is a convertible car seat height marker? ＋
What’s the difference between the upper and lower shoulder height markers? ＋
What’s the difference between an A2 and an A4 convertible car seat? ＋
Which car seat brands have taller rear-facing height markers? ＋
Why did Maxi Cosi recall their A4 seats? ＋
Which seat has the tallest rear-facing marker? ＋
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