Understanding container gross weight

The three numbers

Almost every weight problem in container transport comes from confusing these:

• Tare — the empty weight of the container itself, stencilled on the door. Typically 2.2 t for a 20', 3.8 t for a 40'.
• Payload — the weight of your cargo alone, including its pallets, dunnage and packaging.
• Gross weight — tare plus payload. This is the number the terminal, the shipping line and the road authority all care about.

A fourth number matters on export: VGM, the Verified Gross Mass. Under SOLAS regulations a packed export container cannot be loaded to a vessel without a certified VGM declaration from the shipper. It is the same gross weight, but formally verified — by weighing the packed container, or by adding certified cargo weights to the stencilled tare.

Container rating is not the road limit

Every container carries a maximum payload rating — the most the box can structurally hold. It is nearly always more than the road will allow. A 20' container rated to 28 t of payload will comfortably exceed the legal limit of the combination carrying it, long before it exceeds its own rating.

The binding constraint is the truck, not the box. Total mass across the combination — prime mover, trailer, container and cargo — has to stay within the limit that applies to that combination's axle configuration, and mass has to be distributed correctly across those axles.

The limits that apply in NSW

Under the Heavy Vehicle National Law, a standard six-axle articulated combination operating at general mass limits is capped at 42.5 tonnes gross. Higher figures exist — concessional and higher mass limit schemes, different axle configurations, and Performance Based Standards combinations all change the number — but each brings its own accreditation, route and permit conditions.

Why over-mass is expensive for you, not just for us

Chain of Responsibility law places duties on everyone in the chain, including the consignor and the packer. If a container is packed over-mass, the party who packed it and the party who consigned it carry liability alongside the carrier. Penalties scale with the severity of the breach and apply to each party independently.

In practice this is why we ask for the weight up front and why we will decline a job rather than run it heavy. It is not caution for its own sake — it is the one risk in this business that lands on your desk as well as ours.

Axle distribution matters as much as total mass

A container can be within total gross limit and still be illegal, because the load inside it sits too far forward or too far back. Concentrated dense cargo at one end of a 40' container will overload one axle group while another runs light. If your cargo is dense and does not fill the container, tell us how it is positioned — it changes which trailer we send.

A worked example

A 40' high cube with a stencilled tare of 3,900 kg is packed with 24,000 kg of cargo. Gross weight is 27,900 kg. That is comfortably inside the container's own rating, and whether the movement is legal then depends on the mass of the prime mover and trailer carrying it, and on how that 27.9 t distributes across the axle groups. Two identical containers can produce two different answers.