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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 limit that decides the load is the lowest of the three, and on US roads that is the truck limit, not the container's rating.
The three limits
1. The container's maximum payload. Stamped on the CSC plate on the door. The International Convention for Safe Containers (CSC), ratified by the United States on January 3, 1978, requires the owner of every container in international transport to have it approved (49 CFR 450.5). Payload is the maximum operating gross weight on the plate minus the tare weight. Because the 40 foot box is heavier empty and its maximum gross weight is not double that of the 20 foot, its payload is not double either.
2. The carrier's or terminal's limit. A service or terminal can set a ceiling below the plate figure, for transshipment moves or because of lifting equipment limits at smaller ports. The booking confirmation states the limit; read it before the load plan is fixed.
3. The road weight limit at each end. This is the limit that binds. Legal gross combination weights for a truck, chassis and container on public roads are set nationally and sit below the container's rating. 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 US road limit in numbers
On the Interstate System, 23 CFR 658.17 fixes the maximum gross vehicle weight at 80,000 pounds (36,287 kg). The maximum on any single axle is 20,000 pounds (9,072 kg) and the maximum on a tandem axle group is 34,000 pounds (15,422 kg). The bridge gross weight formula lowers the vehicle limit where axle spacing is short. States cannot enforce limits below these figures on the Interstate System, tolerances included.
| US federal limit (23 CFR 658.17) | Pounds | Kilograms |
|---|---|---|
| Maximum gross vehicle weight | 80,000 | 36,287 |
| Single axle | 20,000 | 9,072 |
| Tandem axle group | 34,000 | 15,422 |
The 80,000 pounds covers everything on the road: tractor, chassis, container tare and cargo. The cargo allowance is therefore 80,000 pounds minus the tractor, the chassis and the container tare, and each of those three weights comes from a document, not from an assumption. A container whose plate rating exceeds that remainder is legal on the vessel and overweight on the highway.
The cargo weight formula
- Start with the legal road limit at destination for the whole vehicle.
- Subtract the tractor weight and the chassis weight, which the trucker states.
- Subtract the container tare from the CSC plate.
- The remainder is the maximum weight of cargo, packaging, dunnage and pallets.
- Compare it with the plate payload. The lower figure is the load limit.
Dunnage, pallets and securing materials count as cargo weight. Packaging that adds weight to a dense commodity reduces the net cargo the container is allowed to carry.
Container condition and periodic examination
The plate is valid only while the container stays serviceable. Under 49 CFR 452.1, a US owner of an approved container has it examined at intervals of not more than 30 months, and a container approved as new has its first examination within five years of manufacture. A plate without a current examination mark means the container is not eligible for the weight on its face. For hazardous materials, 49 CFR 176.172 requires a current CSC approval plate and a shipper's visual examination before packing: dents deeper than 19 mm (0.75 inch), cracks in structural members and seized door hardware all disqualify the box.
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.
| Method | What is weighed | Documents |
|---|---|---|
| Method 1 | The packed, sealed container on a calibrated scale | Weighbridge ticket, signed VGM declaration |
| Method 2 | Every item of cargo, packaging and dunnage, plus the tare from the CSC plate | Itemized weights, signed VGM declaration |
No VGM, no loading. It is one of the few rules in ocean freight with no discretion attached, and a missing declaration is a cause of a container missing its sailing when the documentation team assumes someone else filed it. The shipper named on the bill of lading owns the declaration, so a forwarder transmitting it needs the weight and the signature from the shipper.
Where each weight comes from
| Weight | Source document | Who supplies it |
|---|---|---|
| Container tare and maximum gross weight | CSC approval plate on the door | Container owner or carrier |
| Cargo, packaging and dunnage | Packing list and weighbridge ticket | Shipper |
| Verified gross mass | Signed VGM declaration | Shipper named on the bill of lading |
| Tractor and chassis weight | Trucker's scale ticket or equipment record | Trucker |
| Legal road limit | National or state weight regulation (23 CFR 658.17 in the US) | Road authority at each end |
The five weights reconcile in one direction only: cargo plus tare equals the VGM, and VGM plus tractor plus chassis must stay under the legal road limit. A discrepancy between the packing list and the weighbridge ticket is a documentation error that the shipper corrects before the VGM is signed.
Which cargo hits which limit
| Cargo | Limit reached first | Action |
|---|---|---|
| Apparel, furniture, consumer goods | Cubic capacity | Maximize cube; weight is not the constraint |
| Tiles, stone, ceramic | Road weight | Load to the weight formula; the box stays part empty |
| Liquids in drums or flexitanks | Road weight | Confirm the formula before filling |
| Machinery and metal parts | Floor loading and road weight | Spread point loads, block and brace |
| Paper and printed matter | Road weight | Check the VGM before the cut-off |
Dense cargo changes every calculation
Tiles, stone, liquids, machinery, metal and paper hit weight ceilings while the container is still half empty. For those commodities:
- Two 20 foot containers carry the cargo legally when one 40 foot would be overweight, because the weight is split across two vehicles.
- 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.
- The cargo bills on weight in LCL: the revenue tonne rule charges the greater of one cubic meter or 1,000 kg, as explained in chargeable weight in ocean freight.
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.
Worked example: the revenue tonne
Interworld Freight prices Miami LCL on a 5 CBM and 1,500 kg basis. At 1,500 kg the cargo weighs 1.5 tonnes, below the 5 revenue tonnes its volume represents, so it bills on volume. The same 5 CBM weighing 6,000 kg is 6 revenue tonnes and bills on weight. A shipper who plans the freight budget from cubic meters alone is short by one tonne of freight on the second load. See how LCL container shipping works for the full billing sequence.
Overweight consequences
- Fines at the port gate and on the highway.
- Refusal to load at origin when the VGM exceeds the plate or the carrier limit.
- Re-stripping and re-stuffing costs at the port, paid by the cargo.
- Delay to the sailing and the demurrage that follows, covered in demurrage and detention.
- 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. List dunnage and pallets on the packing list with their weights so Method 2 is auditable. Build the VGM submission into the booking checklist so it is never the reason a container waits. For hazardous cargo, the container also has to meet the condition rules in dangerous goods in ocean freight.
FAQ
What is the maximum weight for a 20ft container?
The CSC plate on the container states its maximum operating gross weight and tare; payload is the difference. The practical maximum is lower on the road: the 80,000 pound US federal limit covers tractor, chassis, container and cargo together.
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. It is determined by weighing the packed container, or by adding the weight of every item to the container tare.
Who is responsible for the VGM declaration?
The shipper named on the bill of lading, using one of the two permitted weighing methods and signing the declaration before the carrier's cut-off.
What is the US federal limit for a loaded container truck?
23 CFR 658.17 sets 80,000 pounds (36,287 kg) gross vehicle weight on the Interstate System, 20,000 pounds on a single axle and 34,000 pounds on a tandem axle group.
What happens if a container is overweight at destination?
It is refused for road transport, requiring stripping and partial reloading at the port, at the cargo's cost.
How often must a container be examined to keep a valid CSC plate?
US owners examine approved containers at intervals of not more than 30 months, and a container approved as new has its first examination within five years of manufacture (49 CFR 452.1).
Do pallets and dunnage count toward the cargo weight?
Yes. Pallets, dunnage, bracing and packaging all add to the cargo weight, and Method 2 of the VGM requires each of them to be weighed or itemized. A heavy pallet type reduces the net cargo the container is allowed to carry.
Is a CSC plate required on every container?
Every container used in international transport must be approved under the CSC (49 CFR 450.5), and the approval is shown on the plate fixed to the container. A container without a current plate is not eligible for the weight it would otherwise carry.
Shipping dense cargo where the weight limit decides the plan? Send us the load details and we will check the limits at both ends.
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