20ft container: how many tonnes of rice, sugar or oil?

The question comes up constantly in food trading, and the answer is never a single figure. Two ceilings coexist: the container’s internal volume and the mass it is allowed to carry. A third, sometimes lower, is set by the road leg at destination. Depending on the product’s density and packing, one or the other sets the tonnage. The figures below are orders of magnitude taken from public data sheets in 2026, not guarantees.

What the standard and carrier data sheets say

ISO 668 sets the external dimensions and maximum gross mass of series 1 containers. In its 2020 edition as amended in 2022, it allows up to 36,000 kg gross for both 20ft and 40ft units. The figure binding on a given container, however, is the one on its CSC safety approval plate, and the data sheets published by shipping lines commonly show 30,480 kg for a standard box.

Two lessons follow. First, a 40ft does not carry twice as much as a 20ft: its payload is of the same order, sometimes lower. A dense product such as sugar therefore gains nothing by travelling in a 40ft. Second, each container has its own tare: the carriers themselves state that their data sheets are indicative and that individual containers vary.

Container limit versus road limit

A 28 t payload remains a theoretical ceiling. The container then has to leave the port by road: maximum vehicle combination mass, axle load and overall height of the laden vehicle are set by each country, and one shipping line notes in its public information that weight limits can vary by country. In a corridor with stricter road rules, a 20ft of sugar loaded to full payload can be held at the port gate or require partial unloading. The right method is to ask the destination forwarder for the maximum gross weight allowed on the final leg, then work back to the cargo tonnage, not the other way round.

Orders of magnitude by product

The table below applies to a standard 20ft loaded without pallets. Tonnages are calculated from an internal volume of about 33 m³, a payload of about 28 t and published stowage factors, meaning the volume taken up per tonne of cargo: 1.13 to 1.34 m³/t for white sugar in bags, 1.39 to 1.45 m³/t for white rice, 1.5 to 1.85 m³/t for canned goods in cartons. The actual tonnage depends on the bag, the stacking, the equipment supplied and the road limit at destination.

For oil, two separate calculations apply. In a flexitank, a single-use bladder of 10,000 to 24,000 litres fitted inside a 20ft, the weight carried depends on density: about 0.9 kg per litre for sunflower oil, or roughly 21 to 22 t for 24,000 litres. Current practice is not to exceed 24,000 kg of liquid in a 20ft, and some carriers set lower ceilings. In bottles, cartons, air and plastic take up the volume: according to a P&I club’s data, a flexitank carries about 50% more than a bottled load, hence an order of magnitude of 14 to 15 t. The flour figure is the least precise in the table: it depends heavily on the bag and on settling.

VGM, pallets and dunnage

Since July 2016, SOLAS regulation VI/2 has required the shipper to provide the verified gross mass (VGM) of every packed container before it is loaded on board. Two methods are allowed: weighing the packed and sealed container, or weighing all packages, pallets, dunnage and securing material and adding the container’s tare, using a certified method. Without a VGM the container should not be loaded, and regulation VI/5 prohibits loading a container whose gross mass exceeds the maximum shown on its CSC plate.

• Palletisation — it speeds up stuffing and unstuffing but uses volume and payload. With an internal length of about 5.90 m and a width of 2.35 m, a 20ft takes eleven 1,200 × 800 mm Euro pallets on a single tier. For rice and sugar, hand-stacking bags without pallets maximises tonnage at the cost of longer handling.
• Big bags — for sugar or flour bound for industrial users, they reduce the number of packages to handle but leave more empty space at the top of the container.
• Dunnage — airbags, boards and chocks fill voids to stop bags and cartons from shifting; their weight counts in the VGM. The load must be spread along the full length of the floor.
• Moisture — sugar, rice and flour are sensitive to condensation. A dry, clean container, kraft paper lining and desiccant bags limit the risk on long voyages.

What to settle before ordering

1. The net tonnage per container and the quantity tolerance, stated in the contract.
2. The maximum gross weight allowed on the final road leg, confirmed by the destination forwarder.
3. Packing: unit weight of the bag or carton, palletised or not, number of packages.
4. The container type, 20ft, 40ft or 40ft high cube, and the condition required for food cargo.

This article does not constitute legal advice; the regulations of the destination country prevail. Every SELA INTERNATIONAL LTD offer states the packing, the number of packages and the net tonnage per container, under the agreed Incoterms® 2020 rule and named place.