A standard 6×4 box trailer is rated to 750kg ATM. Once you subtract the trailer’s own weight (usually around 250-300kg), that leaves roughly 450-500kg of actual load. That is about a cubic metre of soil, a decent trailer-load of green waste, or a fridge and a few boxes. Here is how trailer capacity actually works, what the common sizes carry, and how to check your car can legally tow it.
The three numbers that matter
- ATM (Aggregate Trailer Mass) — the most the trailer is allowed to weigh fully loaded, including its own weight. This is the legal ceiling.
- Tare — what the empty trailer weighs. A galvanised cage, a tipper kit or ramps all add to it.
- Payload — what you can actually put in. Payload = ATM minus Tare.
Most people asking how much a 6×4 can carry want the payload, not the ATM — and the two are several hundred kilograms apart.
Capacity by trailer size
| Size | Axle | Typical ATM | Brakes needed? |
|---|---|---|---|
| 6×4 | Single | 750kg | No |
| 7×4 | Single | 750kg | No |
| 7×5 | Single | 750kg | No |
| 8×5 | Tandem | 2,000kg | Yes |
| 9×5 | Tandem | 2,000kg | Yes |
| 10×5 / 10×6 | Tandem | 2,000-2,800kg | Yes |
| 12×6 | Tandem | 2,000-2,800kg | Yes |
| 12×7 | Tandem | Up to 3,500kg | Yes |
To get your payload, subtract the tare from the ATM. Tare varies with the build — a cage, tipper kit or heavier chassis all add weight — so always use the figures on your trailer’s compliance plate rather than a general guide. If you are unsure, we can tell you the exact tare and ATM for any trailer we build.
The 750kg rule
In Australia a trailer over 750kg ATM must have brakes. That single line explains why the 6×4, 7×4 and 7×5 are built to exactly 750kg: it keeps them unbraked, simpler and cheaper, and towable by most family cars. Step up to a tandem and you gain a lot of capacity, but brakes become mandatory. Our guide to mechanical vs electric trailer brakes covers what that means in practice.
What your car can tow matters just as much
The trailer’s ATM is only half the equation. Your vehicle has its own braked and unbraked towing capacity and a maximum towball download, all in the owner’s handbook. Your real limit is whichever is lower — the trailer’s ATM or your car’s rated capacity. Many small cars are limited to 750kg unbraked, which is another reason the 6×4 is so common.
Load matters too: aim for roughly 10% of the total load weight on the towball, with the heaviest items over the axle. Our guide to towing safely on Australian roads covers loading and sway.
What 450-500kg actually looks like
- Garden and green waste — a full 6×4 with a cage, comfortably within limits.
- Soil, sand or mulch — roughly a cubic metre. Wet soil is heavy, so this is where people most often overload.
- A small move — fridge, washing machine and several boxes.
- Tools and materials — a decent tradie load, though a tandem suits daily work better.
Dense material is the trap. A 6×4 will physically hold more soil or pavers than it is legally allowed to carry — the space runs out well after the weight does.
When to size up
If you regularly carry more than about 450kg, tow long distances, or move machinery, a tandem is the better buy. The extra axle brings capacity and far better stability at highway speed. If your loads are occasional and light, a 6×4 remains the most practical and economical trailer on the road.
Browse our 6×4 trailers, or see how the sizes compare in our trailer sizes and dimensions chart.
Built in Melbourne
U Beaut has been building trailers for around 30 years from our Seaford workshop, using steel from Bluescope in Braeside and Aussie-made components wherever we can. Every trailer carries a compliance plate with its exact ATM and tare. We also handle trailer repairs and servicing in-house.
Not sure what capacity you need? Call us on (03) 9708 2691 or get in touch and we will match a trailer to the loads you actually carry.
How much weight can a 6×4 trailer carry?
A standard 6×4 is rated to 750kg ATM. After subtracting the empty trailer weight (typically 250-300kg), the usable load is around 450-500kg. Check your compliance plate for the exact figures.
What is the difference between ATM and payload?
ATM is the maximum the trailer may weigh fully loaded, including itself. Payload is what you can put in it: payload = ATM minus tare. A 750kg ATM trailer does not carry 750kg of cargo.
Do I need brakes on a 6×4 trailer?
No. In Australia brakes are required above 750kg ATM, and a standard 6×4 sits at exactly 750kg, so it is legally towable unbraked.
How much weight can an 8×5 tandem trailer carry?
An 8×5 tandem is typically rated to 2,000kg ATM. Subtract the tare (heavier than a single axle because of the second axle and brakes) for the usable payload. Brakes are mandatory at this rating.
Can my car tow a fully loaded 6×4?
Check your vehicle’s handbook for its unbraked towing capacity and maximum towball download. Your real limit is whichever is lower — the trailer’s ATM or your car’s rating. Many small cars cap out at 750kg unbraked.
How much does a cubic metre of soil weigh?
Roughly 1,200-1,500kg when dry and more when wet — well beyond a 6×4’s legal capacity. Dense materials like soil, sand and pavers are the most common cause of overloading, because the trailer holds more than it can legally carry.
What happens if I overload a trailer?
Overloading risks fines, voided insurance, and real safety problems — longer braking distances, sway, and accelerated wear on bearings, springs and tyres. Stay within the ATM on the compliance plate.
