Shipping Container

What it means

The FHWA freight glossary describes a container as a "box" typically ten to forty feet long, used mainly for ocean freight, that is loaded onto truck chassis or railroad flatcars for the trip to and from ports.^[1] Because the box itself moves between modes, the cargo is packed once at origin and unpacked once at destination.

The design is standardized by a family of ISO standards. ISO 668 sets the dimensions of series 1 containers, including where the corner fittings sit, and the maximum gross mass for each type. ISO 6346 covers the codes and markings painted on every box. ISO 1496 sets the specifications and tests, with Part 1 for general cargo containers, Part 2 for thermal (refrigerated and insulated) containers and Part 3 for tank containers.^[2]

Shipping container sizes

Ocean carriers mainly run three dry sizes, plus a 45-ft high cube on some trades. The figures below are one carrier's published fleet specifications.^[3]

Source: Maersk dry container specifications.^[3] Other carriers and container series differ slightly, so check the plate and markings on the actual box.

Notice that the 40-ft high cube adds about 9 cubic meters of space but no extra payload: its maximum payload is slightly lower than the standard 40-ft because the box weighs more.^[3] The 20-ft box is the basis of the TEU, the twenty-foot equivalent unit used as the standard measure of containerized cargo.^[1] Full detail on the 40-ft box, including door openings and pallet counts, is on the 40ft container page, and the 20-ft box has its own 20ft container page.

How to read the markings on a container

• Container number. Four letters, six digits and a check digit. The first three letters are the owner code; the fourth is the equipment category, where U means a freight container, J means detachable container-related equipment and Z means a trailer or chassis. The check digit validates the owner code and serial number.^[4]
• Size and type code. A four-character code under ISO 6346. The first character gives length (2 for 20 ft, 4 for 40 ft), the second gives height (2 for 8 ft 6 in, 5 for a 9 ft 6 in high cube), and G1 means a general purpose container. So 22G1 is a standard 20-ft, 42G1 a standard 40-ft and 45G1 a 40-ft high cube.^[5]
• Weights. U.S. rules require every intermodal container to be permanently marked with its empty weight, the maximum cargo weight it is designed to carry, and the sum of the two.^[6]
• CSC safety approval plate. Any container used in international transport must carry a valid CSC plate, usually riveted on the left door. It shows the approving country, the manufacture date, the maximum payload and the stacking test load.^[7]

Types of shipping containers

Most freight moves in dry, general purpose boxes. ISO 1496 also covers thermal containers, which include reefers for temperature-controlled cargo, and tank containers for bulk liquids.^[2] Open-top and flat-rack designs exist for out-of-gauge cargo that will not fit through standard doors or under a standard roof.

Why it matters

The box decides how much freight fits, how heavy the load can be and how it gets unloaded. A floor-loaded 40-ft high cube can take hours of manual labor to empty, while a palletized load comes off with a forklift. RapidShips devans 20, 40 and 45-ft containers, palletized or floor-loaded, at its East Brunswick, NJ dock serving the Port Newark–Elizabeth corridor.

Example

Illustrative only: an importer of lightweight home goods compares a 40-ft standard with a 40-ft high cube. Using Maersk's published figures, the high cube offers 76 cubic meters instead of 67, while payload stays near 28,600 to 28,800 kg.^[3] Because the cartons are light, the shipment runs out of space long before weight, so the high cube carries more product per box. A shipper of dense ceramic tile would gain nothing, because it hits the weight limit first.

Frequently asked questions