A 40′ container is twice the length of a 20′ container..
If I can pack 21 tons of cargo in a 20′ container, I can pack 42 tons of cargo in a 40′ container right..??
Wrong..?? Why is that so..??
A common question asked by many.. If you take a look at the Generic Container Dimensions table, you can see the external dimensions, internal dimensions, max payload and capacity for the various sizes and types of containers..
Based on the structural integrity, design, weight distribution and weight to volume ratio, each of these size/type of containers are designed to carry specific cargo types..
- 20′ containers are designed to carry more weight than voluminous cargo.. Example – Minerals, Metals, Machinery, Sugar, Paper, Cement, Steel Coils all of which are heavy cargoes..
- 40′ containers are designed to carry voluminous cargo rather than heavy cargo.. Example – Furniture, Steel Pipes, Paper scrap, Cotton, Tobacco all of which are voluminous cargoes..
While you cannot pack double the 20′ cargo weight into a 40′ container, you can definitely pack more than double the 20′ cargo volume into a 40′ container..
This is possible due to the volume-to-payload ratios.. As per the generic volume to payload ratio provided by the container manufacturers,
- for 1 ton of weight on a 20′ container a volume of 1.54 m³ can be packed and
- for 1 ton of weight on a 40′ container a volume of 2.53 m³ can be packed
In a 20′ container designed to be packed with 33.50 m³ of cargo, a cargo weight of 21.75 tons can be loaded.. Of course there are heavy tested 20′ container units capable of loading upto 27.50 tons cargo but still the same cubic capacity as these containers are modified to carry such ultra heavy cargoes..
But in a 40′ container designed to be packed with 67.70 m³ of cargo, a cargo weight of only 26.70 tons can be loaded..
In a 40′ high cube container, conversely while the volume capacity increases to 76.0 m³ due to the extra height of 1 feet, the cargo weight capacity remains around 26.50 tons mark due to the increase in tare weight of the 40′ high cube..
Please note that these weights are generic and the actual weights/volumes may vary based on the shipping line..
You might also want to read these two previous articles on this blog :
Do you have any live cases or anecdotes relating to container size/type choice and packing you would like to share..??