Guide

Container loading and what actually fits.

Every quotation eventually turns into a question about how much goes in a container. The cubic capacity figures in circulation disagree with each other, and none of them describe the box you will actually be given. What decides a load is weight, geometry and the carrier's own specification.

The boxes.

Internal dimensions follow the ISO series and are consistent between sources. Cubic capacity and payload are not, so they are missing here on purpose. Ask the carrier for the specification of the container they will actually give you.

20 ft standard: Roughly 5.9 m long, 2.34 m wide and 2.39 m high inside. The default for dense cargo, because a full 40 ft of the same goods would exceed the weight limit before it filled.¹
40 ft standard: Roughly 12.03 m long, with the same width and height as the 20 ft. Twice the floor, and not twice the payload.¹
40 ft high cube: The same footprint with about 2.69 m of internal height. The extra 30 cm is what makes it worth paying for on light bulky cargo.¹
Reefer: Smaller inside than the equivalent dry box, because the insulation and the machinery take space. Plan on less room than the dry equivalent, not the same.¹

What decides the load.

Weight usually stops you first: For coffee, cocoa, charcoal or seaweed the container fills on weight long before it fills on volume. For furniture and homeware it is the other way round.
Geometry costs more than people expect: Cartons that do not tessellate leave air. A load can be physically full at well under the nominal cube, and the difference is money on every shipment.
The destination has its own limit: Road weight rules where the box lands can cap what you may legally move on a truck, whatever the container could carry at sea.

Stuffing and sealing.

A container is loaded at a warehouse or a stuffing station, not at the port. Ports are secure areas for moving boxes, and by the time yours arrives there it is sealed. That is worth knowing when a supplier sends you photographs of goods being carried into a container between rows of stacked units at a terminal.

The seal number goes on the documents and is the first thing checked at the other end. Photographs of the loaded container, the closed doors and the seal in place, taken in sequence, cost nothing and are the cheapest evidence you will ever hold.

Timing matters as much as method. Indonesian holidays close stuffing stations and empty the workforce for weeks:when the country stops working →

Questions buyers ask.

How many cartons fit in a 40 ft container?

Nobody can answer that without your carton dimensions and weight. Send those and a loading plan takes minutes to produce. Any supplier who answers with a round number before asking is guessing, and their guess is what you will be quoted against.

Should I ship 20 ft or 40 ft?

It depends on density. Heavy goods hit the weight limit in a 20 ft, so two of those often beat one 40 ft. Light bulky goods want the 40 ft high cube. The calculation is quick once the product is known and it changes the freight cost materially.

Can I mix products in one container?

Compatible dry cargo, yes, and it is one of the reasons buyers use an agent. What does not mix is anything requiring a different temperature, and anything whose documentation has to stay separate. Regulated goods and cold chain stay in their own boxes.

Who is responsible if the load shifts?

It depends on the Incoterm and on who stuffed the container. Damage from bad stowage is a supplier problem in principle and your problem in practice unless the contract and the inspection record say otherwise. Photograph the load before the doors close.

Need a loading plan?

Send the carton dimensions and weight with the order quantity. We come back with what fits and which box costs least to move it.

Sources

1A guide to shipping container sizes and types. Maersk. Checked 3 August 2026.