When a supplier tells you "this is about half a container", that is a guess by eye. Before you book transport you need two numbers: how big the container is inside, and how much of that space your cartons can really use. They are not the same number.
Container dimensions: 20ft, 40ft and 40HC
The figures below come from Maersk's specification sheet for steel dry containers. Containers from other owners can differ slightly.
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| Measure | 20ft standard (20GP) | 40ft standard (40GP) | 40ft high cube (40HC/40HQ) |
|---|---|---|---|
| Internal length | 5,896 mm | 12,032 mm | 12,032 mm |
| Internal width | 2,350 mm | 2,350 mm | 2,350 mm |
| Internal height (to load line) | 2,393 mm | 2,393 mm | 2,697 mm |
| Door opening width | 2,350 mm | 2,340 mm | 2,340 mm |
| Door opening height | 2,274 mm | 2,274 mm | 2,577 mm |
| Internal volume | 33 m³ | 67 m³ | 76 m³ |
| Tare (empty weight) | 2,280 kg | 3,700 kg | 3,880 kg |
| Maximum payload | 28,200 kg | 28,800 kg | 28,620 kg |
What the table tells you:
- A 40HC is no longer than a standard 40ft. The only difference is height: about 30 cm more inside and about 30 cm more at the door.
- The door is lower than the inside. In a 20ft or standard 40ft you have 2,393 mm inside but only 2,274 mm through the door. A tall pallet or a machine can fit inside and still not get through the door.
- Maximum payload is almost the same for all three. A bigger box does not carry more kilograms.
Under the IMO International Convention for Safe Containers (CSC), approved containers carry a safety approval plate with the relevant technical data. For heavy cargo, the figures for the actual box are the ones that count.
How much actually fits
Catalogue volume is measured in an empty steel box. Your goods are in cartons, and cartons never fill every centimetre. So we plan with practical figures:
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| Container | Internal volume (Maersk) | Practical with cartons |
|---|---|---|
| 20ft (20GP) | 33 m³ | about 30 CBM |
| 40ft standard (40GP) | 67 m³ | confirmed in the quote |
| 40ft high cube (40HQ) | 76 m³ | about 70 CBM |
A 20ft container takes about 30 CBM of cartons in practice. A 40ft high cube container (40HQ) takes about 70 CBM of cartons in practice. For the standard 40ft we do not give one figure up front. What it takes depends on your cartons, so we confirm the practical load in the quote.
Why 33 m³ is not 33 CBM of goods
Carton height
Take a carton 40 cm tall. Six layers make 240 cm, but a 20ft and a standard 40ft are 239.3 cm high inside. The sixth layer does not fit, so about 40 cm stays empty above the fifth layer along the whole length. In a 40HC, at 269.7 cm, six layers fit and about 30 cm is left. The same carton gives a different fill in a different box.
Width and length
Internal width is 235 cm. A carton 60 cm long fits three times across (180 cm) and leaves 55 cm, where you can turn cartons sideways, though rarely perfectly. Every gap along the wall repeats down the full length of the container.
How high cartons can be stacked
Some cartons will not take five or six layers on top. Cartons with glass, lamps or thin walls often carry a stacking limit mark. If the top layers cannot be loaded, that volume stays empty.
Pallets
A pallet takes height and leaves gaps at the walls. Palletised goods are quicker to load and unload, but the same container holds fewer CBM than with hand-stacked cartons.
Weight
Maersk's maximum payload for a 20ft is 28,200 kg. Divided by the practical 30 CBM, that is about 940 kg per CBM. If your goods weigh more than that per cubic metre, for example tiles, metal parts or liquids, the container fills by weight, not by volume. With heavy goods, send the gross weight together with the carton sizes when you ask for a quote.
How to count how many boxes fit
You need the outside dimensions of the carton in centimetres, the number of cartons and the gross weight per carton. Ask the supplier for the packed carton size, not the product size.
- Multiply the carton's length, width and height in cm.
- Divide by 1,000,000. That is the CBM per carton.
- Multiply by the number of cartons. That is the total volume.
- Compare it with the practical container volume, not the catalogue figure.
- Multiply the gross weight per carton by the number of cartons and compare it with the payload.
Example with a 60 x 40 x 40 cm carton:
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| Step | Sum | Result |
|---|---|---|
| CBM per carton | 60 x 40 x 40 / 1,000,000 | 0.096 CBM |
| 10 cartons | 0.096 x 10 | 0.96 CBM |
| 300 cartons | 0.096 x 300 | 28.8 CBM |
| 700 cartons | 0.096 x 700 | 67.2 CBM |
On volume, 300 of these cartons (28.8 CBM) are close to the 30 CBM a 20ft takes in practice, and 700 (67.2 CBM) are close to the 70 CBM of a 40HQ. Near the limit, CBM alone is not enough. This carton is 40 cm tall, so in a 20ft it goes only five layers high and about 40 cm stays empty at the top. Expect fewer than 300 to fit, and send us the carton list before you fix the order quantity.
Instead of doing it by hand, enter the sizes in the CBM calculator. You type length, width and height in cm and the number of cartons, and it gives the total volume in m³. It does not work out weight, so send us the gross weight separately.
If you are buying several items from different suppliers, work out each carton type separately and add the volumes. In our warehouse in China we collect goods from several suppliers and check them, and we document every check with photos and video.
If you are still agreeing terms with the supplier, the Incoterms guide explains who is responsible for the goods up to which point.
LCL or a full container
There is no fixed CBM point where a full container starts. 20 CBM of light goods and 20 CBM of heavy goods are different cases. LCL is charged per CBM, with a minimum of 1 CBM.
Where the goods leave from also depends on the type of transport. A full container (FCL) departs from the appropriate Chinese port, the one nearest the supplier. LCL goods come into our warehouse first and then leave from Ningbo.
The choice is covered in more detail in the LCL or FCL guide. For what goes into the freight price, see container cost from China to the Balkans.
What to ask your supplier before a transport quote
- outside carton dimensions in cm;
- pieces per carton and total number of cartons;
- gross weight per carton;
- whether the goods are palletised, and the pallet height;
- any stacking limit on the cartons;
- what the product is, with a photo of the packed carton.
With this list you can tell whether the goods suit LCL, a 20ft or a 40ft, and how much space is left.
Next step
Put your carton sizes into the CBM calculator and check the total volume. Then look at container shipping from China or LCL consolidation. When you are ready, send us your carton list, gross weight and product description through the contact form, and we will agree the right transport type with you.
