3 Across: The Magic Number

One of the biggest challenges for a growing family is when that third baby comes along – fitting three child restraints across a back seat can be a hugely stressful ordeal, but it doesn’t have to be! There are some tips, tricks and products that can make your life a whole lot easier, and we’ve compiled 7 of the best right here!

Slim Design ProductsStart with the middle restraint.

You want to install the middle restraint first, as it will determine how much space you have on the sides, and it’s easier to install the side restraints last.

Use a rear facing restraint in the middle position.

While it’s nice to be able to have the rear facing restraint on the side for your convenience and comfort, often times you’ll find having two forward facing restraints next to each other will sit awkwardly, or not fit at all. We were lucky enough to fit our rearward facing restraint on the side, but if we had to choose between having it in the middle or a new vehicle, we’d have picked the middle!

It’s ok if your tether straps aren’t quite straight.

If you have to push your restraints over a little to get that last one in, and you find your top tether strap is now at a slight diagonal angle, that’s ok. In fact, the ADR for motor vehicles allows car manufacturers to place anchor points up to 40 degrees offset from the centre of the seating position, so in some vehicles you could potentially see this behaviour with only one or two restraints.

It’s ok if your restraints touch the doors.

If your child restraints contact the doors, that’s ok. Being hard up against the door can actually have some benefits in relation to the reduction of momentum in a side impact accident, and…

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Don’t worry about rear side curtain air bags.

If your restraint is against the door, and your vehicle is equipped with rear side curtain air bags, it’s easy to feel like there could be an issue there – however, while the restraint could potentially interfere with the operation of the rear side curtain air bags, all child restraints sold in Australia must demonstrate side impact protection by themselves. The Australian Standard’s side impact protection requirements are the most stringent in the world, so you can rest assured that your child is protected, side curtain air bag or not.

3 Across in Quattro

Three across – rearward facing in Quattro convertible car seats!

Measure your back seat.

You want to measure across from the top of the windows (to match against the top of the restraints, often the widest part), from the door arm rests (to match against the restraint armrests) and the actual back seat (to ensure you can physically sit three restraints across it).

Choose the right restraints.

We feature all of our child restraint dimensions on their product pages within this website, so you can make informed decisions before you buy. We offer a number of narrow child restraints that can make the three across problem easier for you to solve.

Fitting 3 across the back seat can be a real challenge. Sometimes, nothing will work and the only option will be to look at buying a new, larger vehicle. But with a little homework, some child restraint juggling and the right restraints, you might be able to avoid that particular path (at least until number four comes along!).

Our Three-Across-Friendly car seats and boosters;

Quattro, Attain or Duet (CS8113)- 42cm at it’s widest point (Australia’s slimmest car seat!)
Grandeur, Achieve or Cadence (CS9213)- 44cm at it’s widest point (Australia’s slimmest Type G car seat!)
The Kompressor Series – 44cm at it’s widest point.
Visage – 44cm at it’s widest point.
The Vario Series – 43cm at it’s widest point.
The Versatile Folding Booster – 40cm at it’s widest point.

Good luck, and as always, if you have any questions or comments, we’d love to hear from you!

Leave a comment


  1. Bdaz says

    What about when the middle sear belt is a lap belt not an across shoulder, would that make a difference

    • says

      Hey Bdaz,

      Thanks for contacting us! If the middle seat in your vehicle is only a lap seatbelt, and not a complete lap & sash seatbelt, it is still safe for use with all InfaSecure Child Restraints with the exception of dedicated Booster Seats. Hope this helps! 🙂

  2. l trop says

    I am confused, your oldest appears too large for rear facing position and NONE of the children have chest straps.

    • says

      Hi there,

      Thanks for contacting us! According to our Manufacturer guidelines, the oldest child in this image can remain Rearward Facing until she has outgrown the second shoulder height marker. Once she reaches the second shoulder height marker, she must be turned to Forward Facing. In regards to the chest straps, we do not recommend the use of any After Market Accessories, including chest straps, with any of our restraints. For a more in-depth explanation as to why we don’t recommend the use of chest clips please visit: https://infa.link/chest-clips

      Hope this clarifies things 🙂

    • says

      Hey Liz,

      Thanks for contacting us! We have a range of child restraints that we manufacture that would be suitable for use for 8 to 10-year-olds, fitting them in a 3 across situation would depend on your vehicle. We’ve detailed some of your options below, including the Achieve Premium, Accomplish Premium, Visage Astra and Aspire Premium:

      1) Achieve Premium (CS9213): The Achieve Premium is a Convertible Car Seat that is suitable for use from Birth all the way up to a large 8-year-old, with the use of an internal 6 point harness throughout its entire lifespan. The Achieve is extremely compact, measuring an incredibly narrow 44cm across at its widest point, making it perfect for 3 across installations! The comparable models include Cadence, Grandeur, Titanium & Emperor. Here is a link to our Achieve Premium product page: https://infasecure.com.au/products/achieve-premium/

      2) Accomplish Premium (CS9013): The Accomplish Premium is a Harnessed Car Seat and is suitable for use from 6 months all the way up to a large 8-year-old with the use of a 6 point harness. The Accomplish Premium does, however, measure slightly wider than the Achieve Premium and is more difficult to fit for 3 across installations. The comparable models include Opus, Emerge, Platino, Orbit & Pulsar. Here is a link to our Accomplish Premium product page: https://infasecure.com.au/products/accomplish-premium/

      3) Visage Astra (CS7313): The Visage Astra is a Convertible Booster Seat and is suitable for use from 6 months all the way up to a large 8-year-old. The Visage features the tallest exist height marker on a Convertible Booster Seat in Australia, as well as an adjustable, locking headrest. Here is a link to our Visage Astra product page: https://infasecure.com.au/products/visage-astra/

      4) Aspire Premium (CS6213): The Aspire Premium is a dedicated, tethered Booster Seat that is suitable for use from 4 years all the way up to a large 8-year-old. The Aspire Premium is the tallest Booster Seat on the Australian Market and features an adjustable, locking headrest, which enables the seat to grow with your child. Here is a link to our Aspire Premium product page: https://infasecure.com.au/products/aspire-premium/

      Hope this helps! 🙂

  3. Christie says

    With 3 rear facing like in the photo, how do you get the child into the middle seat? Is it easier to have a younger or older child in that spot?

    • says

      Hey Christie,

      Thanks for contacting us! The best way to get your child into the middle seat in a 3 across rearward facing position would depend on their age and your vehicle. If your child is older, they are able to climb over the other restraints or through the boot into the middle seat, where you can buckle them up by either leaning across the restraints on either side or through the boot of your vehicle if possible. If your child is too young to climb, you can place your child into their seat from either side of the car or through the boot if your vehicle allows this. Hope this helps! 🙂

  4. Sunni Friello says

    The pic says 3 across with the Quattros. I thought the middle seat looked like a Quattro but the outer two looked like Grandeurs? Plus the two kids look bigger than 4. Do my eyes deceive me?

    • Rachel says

      Hi Sunni, this would be deceived eyes due to the design of the vehicles rear seat and the lens used to get the photo, these are indeed all Quattros!

  5. Laura A says

    THANKYOU! I was always worried about my evolves touching the side of the car, They’re a snug fit but glad its not going to decrease the level of safety my 3 cherrubs get 🙂
    Seriously in love with my InfaSecure Seats <3 Thanks for making life easier 😀

    • Cara says

      Do you have three evolves across? What car do you drive, we have one and I am considering buying a second but want to be able to fit a rear facing in there two.

  6. says

    This is great but we are at the stage now where we need a booster seat with adult seatbelt for at least 1 of our 3 kids. There is no room to get hands down between seats to buckle. Please make a seat that is narrow across the back to enable buckling. Even with the folding booster we are struggling because the seat next to it is so big.

  7. Zoe says

    Hello, Just wondered if you have moved your Mr 5 to the booster seat yet and if so, how you manage to do up the seat belt? I am about to fit 3 car restraints in my car and wanted my oldest in a booster seat but to do up the seat belt means sticking my hand down a tight space between car restraints and trying to secure a belt into a buckle that moves…impossible! I have been told not to use seat belt extenders for child restraints but how else can I manage this?? I hope you have some ideas!

    • says

      Hey Zoe! Mr 5 (now Mr 6!) actually graduated into an Evolve last year, so he’s still harnessed. Boosters can be tricky, having to get your hand in to fasten the belt. You need to be looking for seats that are not only narrow, but also have extra-narrow bases (our Kompressors, for instance) – I wish there were an easier answer!

      • Jessica says

        Great to read this!!!! I’m so in love with the evolve and looking at either it or Genesis for my son’s now 🙂 I love that we have this option to help keep our kids safe!