Short answer: Divide each internal container dimension by the matching carton dimension, round each result down, and multiply the three numbers. Check the result against the container's load capacity in cubic metres and its payload in kilograms. This floor-loading arithmetic ignores pallets and door clearance, so a forwarder confirms the real count.
Internal dimensions from one carrier
| Container | Internal length (m) | Internal width (m) | Internal height (m) | Load capacity (m3) | Payload (kg) |
|---|---|---|---|---|---|
| 20 ft dry | 5.898 | 2.350 | 2.390 | 33.1 | 28,330 |
| 40 ft dry | 12.032 | 2.350 | 2.390 | 67.6 | 26,840 |
| 40 ft high cube dry | 12.032 | 2.350 | 2.695 | 76.2 | 28,800 |
From Ocean Network Express dry container table [1]. Wikipedia gives slightly different ISO figures, for example 5.867 m internal length for a 20 ft box and 11.998 m for a 40 ft box, so carriers differ and the line you book governs [2].
Six steps
- Take the carrier's internal dimensions. Use the internal length, width and height from the shipping line for the container you will book.
- Measure the packed carton. Use the outer carton length, width and height in metres, not the product size.
- Divide and round down. Divide each container dimension by the carton dimension on the same axis and round each result down to a whole number.
- Multiply. Multiply the three whole numbers to get cartons for that orientation.
- Try each orientation. Repeat with the carton turned, and keep the highest count.
- Check volume and weight. Compare total carton volume with the load capacity and total weight with the payload, then ask the forwarder to confirm.
Worked example with an invented carton
Example only, not ArtzFolio's price or terms. Carton 0.60 x 0.40 x 0.10 m. These dimensions are an arithmetic example, not a product specification.
| Container | Orientation 1 | Orientation 2 | Orientation 3 |
|---|---|---|---|
| 20 ft dry | 1035 | 966 | 1035 |
| 40 ft dry | 2300 | 2070 | 2300 |
| 40 ft high cube dry | 2600 | 2340 | 2760 |
- Orientations: 1 = Length 0.60 along the box, width 0.40 across, height 0.10 up; 2 = Length 0.40 along the box, width 0.60 across, height 0.10 up; 3 = Carton stood on its 0.40 side (0.60 along, 0.10 across, 0.40 up)
- In the 40 ft high cube, orientation 1 gives 20 x 5 x 26 = 2600 cartons
- Those cartons occupy 62.4 m3 of the 76.2 m3 load capacity, about 82 percent, because each division is rounded down
- The payload of 28,800 kg divided by 2600 cartons leaves about 11.1 kg per carton before the weight limit binds
Pallets change the count, so read pallet sizes for export cartons. Carton weight can be estimated with the framed piece weight calculator.
Questions answered
How do I estimate cartons per container?
Divide each internal container dimension by the carton dimension, round down, multiply the three numbers, then check volume and weight against the container's load capacity and payload.
Why do carrier and Wikipedia dimensions differ?
Carrier containers vary slightly; the ONE table lists 5.898 m internal length for a 20 ft dry box while Wikipedia gives 5.867 m. Use the figures of the line you book.
Does this method include pallets?
No. It is floor-loading arithmetic and ignores pallets, door clearance and stacking limits; a forwarder confirms the real count.
Further reading
- Shipping Container Size and Dimensions (dry containers), Ocean Network Express (ONE)
- Intermodal container, Wikipedia
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General information, not legal, customs or tax advice. Your written quote and contract govern. Examples use invented numbers unless stated otherwise.