Three different weight limits apply to the same full container, and they bind in a sequence most shippers only discover when a loaded box cannot legally leave the port. The container's own rating is usually the least restrictive of the three.
The three limits
1. The container's maximum payload. Stamped on the CSC plate on the door. A standard 20 foot container typically allows a payload in the region of 28,000 kg and a 40 foot around 26,000 to 28,000 kg, with the exact figure varying by unit. Because the 40 foot box is heavier empty, its payload is not double the 20 foot.
2. The carrier's or terminal's limit. Some services and terminals impose lower ceilings than the plate, particularly for transshipment or for lifting equipment constraints at smaller ports.
3. The road weight limit at each end. This is the one that binds. Legal gross combination weights for a truck, chassis and container on public roads are set nationally and are far lower than the container's rating in most jurisdictions. A container that is legal on the vessel can be illegal on the road at destination, and the cost of stripping and re-loading falls on the cargo.
The practical result: a 20 foot container often reaches its usable weight around 18 to 22 tons of cargo depending on the road rules at both ends, well below the plate figure.
Verified gross mass
Under the SOLAS amendments, the shipper must provide the verified gross mass of a packed container before it can be loaded aboard a vessel. Two methods are permitted: weigh the packed container, or weigh the cargo and packaging and add the container tare from the plate. The declaration must be signed by the shipper and submitted before the carrier's cut-off.
No VGM, no loading. It is one of the few rules in ocean freight with no discretion attached, and it is a common cause of a container missing its sailing when the documentation team assumes someone else filed it.
Dense cargo changes every calculation
Tiles, stone, liquids, machinery, metal and paper hit weight ceilings while the container still looks half full. For those commodities:
- Two 20 foot containers frequently move the same cargo more cheaply than one 40 foot, because the weight can be split legally.
- Blocking and bracing matter more, since a partially filled heavy load shifts.
- Floor loading limits inside the container apply, especially for concentrated point loads from machinery.
If your cargo is dense, the LCL and FCL comparison in LCL vs FCL for US exports crosses over earlier than the volume rule suggests.
Overweight consequences
Fines at the port gate. Refusal to load. Re-stripping and re-stuffing costs. Delay to the sailing and the demurrage that follows, which is covered in demurrage and detention. On the road, liability exposure if an overweight vehicle is involved in an incident.
Practical steps
Read the CSC plate for tare and payload rather than assuming a standard figure. Confirm the road limit at destination before planning the load, not after. Weigh, do not estimate, and keep the weighbridge ticket. Build the VGM submission into the booking checklist so it is never the reason a container waits.
FAQ
What is the maximum weight for a 20ft container?
The plate on the container states its maximum payload, commonly around 28,000 kg, but road limits at origin or destination usually reduce the practical maximum well below that.
Why can a 40ft container not carry double a 20ft?
Its tare weight is higher and its maximum gross weight is not proportionally larger, so the payload is similar rather than double.
What is VGM?
Verified gross mass, the shipper's declared weight of the packed container required before loading under SOLAS.
Who is responsible for the VGM declaration?
The shipper named on the bill of lading, using one of the two permitted weighing methods.
What happens if a container is overweight at destination?
It may be refused for road transport, requiring stripping and partial reloading at the port, at the cargo's cost.
Shipping dense cargo where the weight limit decides the plan? Send us the load details and we will check the limits at both ends.