Choosing the right container: dimensions, capacity and when to use each type

The container is the unit of cost in sea transport. Choosing the wrong type means paying for empty space, or finding at the port that the cargo does not fit or exceeds the permitted weight.

The most common formats

The values below are indicative. They vary slightly by manufacturer and carrier and should be confirmed before finalising load planning. Payloads and volumes are the maximums Maersk publishes, and it warns that specific limits vary by country.

Internal width is about 2.35 m in all of them. A 20ft container is one TEU (twenty-foot equivalent unit); a 40ft is two.

More volume or more weight?

Light, bulky cargo, such as furniture or packaging, uses up volume before weight: the 40ft High Cube suits. Dense cargo, such as metal parts, tiles or packaged liquids, uses up weight before volume: two 20ft containers are often better than one 40ft, because the weight is spread out and inland road transport may have lower limits than shipping.

Special types

• Refrigerated (reefer): holds a set temperature; the range depends on the unit (Maersk, for example, states −60 °C to +30 °C). It needs electrical connection on the ship, at the terminal and on the truck.
• Open top: removable roof, for cargo loaded from above, such as tall machinery.
• Flat rack and platform: no side walls, for heavy or out-of-gauge cargo. Out-of-gauge goods pay surcharges and need specific planning.
• Tank (ISO tank): for bulk liquids, including chemicals and food products.
• Ventilated: for cargo that gives off moisture, such as coffee or cocoa.

FCL or LCL

If the cargo does not fill a container, it can travel as LCL (less than container load), consolidated with other customers' cargo. It is charged on the greater of weight in tonnes and volume in cubic metres, at one tonne to one cubic metre. As volume grows, FCL (full container) tends to be cheaper per unit, faster and with less handling. LCL has more consolidation and deconsolidation steps, which can add days and risk of damage.

Before you commit

• Ask for the dimensions and weight of each package as packed, not of the unpacked goods.
• Confirm the maximum weight allowed at the destination port and on the roads to the customer.
• Distribute weight evenly and secure the cargo. Poorly stowed cargo is the main cause of container damage.
• Declare the verified gross mass, mandatory before loading on the ship (SOLAS rule).

Cover photo: Virtual-Pano, CC BY 4.0, Wikimedia Commons.