A 40ft container is twice as long as a 20ft container and has roughly twice the volume (67 m³ versus 33 m³), but the payload it can carry is almost the same; for both, the maximum gross weight is usually 30,480 kg. For this reason heavy, dense cargo goes into a 20ft container, and light, bulky cargo into a 40ft container.
Dimension and weight differences at a glance
The external dimensions of containers and the upper limits of their maximum permitted gross weight are defined in the ISO 668 standard; each container's own values are shown on the CSC plate on its door. Width and standard height are the same for both sizes; the difference is in length. Internal dimensions vary by a few centimetres depending on the manufacturer.
| Feature | 20' standard (DC) | 40' standard (DC) |
|---|---|---|
| External length | 6.058 m | 12.192 m |
| Internal dimensions (L × W × H) | 5.90 × 2.35 × 2.39 m | 12.03 × 2.35 × 2.39 m |
| Volume | about 33 m³ | about 67 m³ |
| Tare | about 2,200–2,300 kg | about 3,700–3,800 kg |
| Maximum payload | about 28,000 kg | about 26,500–28,800 kg |
| Maximum gross weight (typical) | 30,480 kg | 30,480 kg |
| Euro pallets (single layer) | 11 | 23–24 |
| TEU equivalent | 1 TEU | 2 TEU (1 FEU) |
For other types, see container types and dimensions.
What do TEU and FEU mean?
TEU (twenty-foot equivalent unit) is a measure that treats a 20-foot container as one unit. A 40ft container counts as 2 TEU or 1 FEU (forty-foot equivalent unit). Ship capacities, port handling statistics and some terminal charges are expressed in TEU. A 24,000 TEU vessel can theoretically carry 24,000 twenty-foot or 12,000 forty-foot containers; in practice, weight and the stowage plan reduce this number.
Why choose a 20ft container for heavy cargo?
Both containers carry roughly the same weight. Because the tare of a 40ft container is 1.5 tonnes higher, its net payload is sometimes even lower than that of a 20ft. Cargo density is a good guide for the decision:
- A 20ft container carries 28 tonnes of cargo in 33 m³; that is about 850 kg per cubic metre.
- A 40ft container carries 26.5 tonnes of cargo in 67 m³; that is about 400 kg per cubic metre.
- Cargo with a density above 400 kg/m³ brings a 40ft container to its weight limit before its volume is full. With steel, ceramics or marble at around 800 kg/m³, half the volume of a 40ft remains empty; a 20ft is more efficient for such cargo.
For light, bulky products (furniture, textiles, insulation), a 40ft container or a high cube container with an internal height of 2.70 m is more economical.
How does the road weight limit affect the choice?
The weight a container can carry and the weight that can be transported by road are not the same. In Türkiye, Article 128 of the Road Traffic Regulation (Karayolları Trafik Yönetmeliği) sets the maximum laden weight of a tractor and semi-trailer combination carrying an ISO container at 44 tonnes. After deducting the tare of the tractor, chassis and container, the cargo that can be carried by road is around 26–27 tonnes. A heavy 20ft container, on the other hand, concentrates its load on a short area, so it must be positioned evenly over the chassis axles. For planning transport from the port to the factory, see moving containers by road.
How does the freight rate change?
Ocean freight is quoted per container. The freight for a 40ft is usually not twice that of a 20ft; this is why a 40ft is cheaper per cubic metre for bulky cargo. Port and terminal charges, however, are often tariffed separately by container size.
Common mistakes
- Loading heavy cargo into a 40ft and exceeding the road weight limit
- Not checking the maximum gross weight on the CSC plate on the container door
- Delaying the VGM (verified gross mass) submission before loading onto the vessel
- Concentrating the cargo at one end of the container
How does Voltim Global support this?
For container transport and sea freight requests, Voltim Global assesses the weight and volume of the cargo together and also factors the road limit between the port and the delivery point into the container choice.