Shipping Container Size: 20ft, 40ft and 40 High Cube Compared

Alan Xiao Founder, Sourcing Pioneer

· Updated October 24, 2026 · 11 min read

Shipping container size is quoted three ways, and only one of them decides what you can load. The outside length gives the name, the inside length gives the cargo, and the door opening decides whether the cargo goes in at all. A 40ft box is 12.03 m inside. If your machine is 2.5 m tall, a standard 40ft will not take it, and a high cube will. Here is the practical comparison, and the four questions that pick the box.

The Short Answer

Three sizes cover almost every shipment. The 20ft holds about 33 cubic metres. The 40ft holds about 67. The 40 high cube holds about 76, because it is roughly 30 cm taller.

All three are about 2.35 m wide inside, so width almost never changes the choice. Length and height do.

Pick by cargo, not by habit. Dense cargo that weigh out before they fill the box want a 20ft. Light cargo that fill the box before they reach the weight limit want a 40ft. Tall or bulky cargo want the high cube, but only if the door clears them.

One warning before the numbers. Every figure below is the figure carriers publish. The box you actually get is a used steel box with dents, and its inside measurements can be a few centimetres off. Plan against the smaller number.

Outside, Inside and Door

Three measurements, three different jobs, and mixing them up is the most common planning error.

Outside

The name of the box and the space it takes on the ship. A 40ft is about 12.19 m long outside. This number never decides what you can load.

Inside

The usable floor and height. This is where cubic capacity comes from, and it is what you compare against your cargo volume.

Door

The clear opening when the doors are folded back. A load wider or taller than the door will not enter, even if it would fit inside once it is in.

The door figure is the one buyers forget. A crate can pass the volume test, pass the height test against the internal height, and still stop at the door frame by two centimetres.

The Three Sizes Side by Side

Width sits at about 2.35 m inside for all three. That is why nobody chooses a box by width, and why a 2.4 m wide load becomes a special case, not a bigger booking.

The high cube earns its place on height alone. It is the same length and the same width as a 40ft standard. The extra 30 cm of internal height is the whole difference, and it is worth about 9 cubic metres.

Pallet counts follow from the floor. A 20ft takes about ten Euro pallets in one tier, or nine standard pallets. A 40ft takes about twenty or twenty-one Euro pallets, or twenty standard pallets. Stack them two high and the capacity doubles, provided the cargo allows it.

The Door Trap

A high cube is only useful if the load can pass the door. The door on a high cube is taller than on a standard box. It is still shorter than the internal height, and the gap is small enough to catch a tall crate.

So measure the door first when the cargo is tall, then check the internal height. If the door is the limit, the extra cube above the door line is space you have paid for and cannot use.

Two practical fixes exist. Build the crate in two parts and join it inside, which costs labour and adds a joint. Or book a flat rack, which has no roof and no sides, and pays for the space in a different way.

Wide loads have the same problem with a different frame. The door width, not the internal width, decides whether a wide crate enters, and the gap between them is narrow.

Weight: The Limit That Is Not in the Brochure

A container has a payload rating. That rating is not the limit that decides your load, and this is where light cargo and dense cargo part company.

Take a 20ft box. The box itself weighs a couple of tonnes, and the payload figure stamped on it is generous. On paper it can carry far more than most roads allow.

Road law then cuts it down. Many countries cap a loaded truck and trailer at about 40 tonnes gross, and the container's payload does not override that. A heavy cargo in a 20ft will hit the axle limit long before it hits the box limit.

So run two numbers, not one. The cargo weight against the container payload, and the loaded vehicle weight against the road limit. The smaller answer wins.

This is exactly why dense cargo ship in 20ft boxes. A full 40ft of the same dense cargo would exceed the road limit. The second half would be empty air, and you would still pay for it.

Light cargo has the opposite problem. Foam, packaging, soft furnishings and hollow plastic fill a 40ft long before they reach half the weight limit. For those, volume decides the booking and weight is irrelevant.

One more rule runs alongside weight, and it has no workaround. Before a box is loaded, its packed weight must be declared and verified, and the ship will not load a box without that figure. The number has to come from a weighbridge or from a documented weighing method, not from adding up carton labels.

This catches small importers who estimate. If the declared weight is wrong, the box is held at the gate, and the cost of the hold lands on the shipper. Weighing is cheap. A refused box is not.

Two regional variants are also worth knowing about. A 45ft high cube exists in some trades, with more length and the same extra height, and it is common on North Atlantic routes. A pallet-wide box is the same length but wider inside, built so two Euro pallets sit side by side without wasting a strip of floor.

Four Questions That Pick the Box

Work through these in order. The first question that gives a hard answer makes the decision.

One

Does the load pass the door? If not, change the packing or change the box. Volume arithmetic does not help here.

Two

Does it weigh out before it fills up? If yes, a 20ft is usually cheaper per tonne, and a 40ft wastes payload.

Three

Does it fill up before it weighs out? If yes, a 40ft is the cheaper box per cubic metre, and the high cube is even cheaper if the cargo stacks above 2.39 m.

Four

Does it fit a sensible loading plan? Check the pallet counts. A load that leaves three metres empty in a 40ft may still be cheaper than two 20ft boxes, or the other way round.

The booking terms decide who pays the freight and where the risk changes hands, and they change the cheapest box. Read how CIF and FOB move cost and risk before you compare two quotes.

Most buyers I work with settle into one habit, usually 40ft because it feels efficient. The habit costs money on dense cargo and on small trial orders. Run the questions again for each new product, because the answer changes with the cargo.

A trial order of two cubic metres does not need a container at all. It needs the shared-space option instead of a full box. Booking a 20ft for that volume is the most common way small importers overspend.

Check the Box You Actually Get

Every container carries an owner code and a serial number. The last digit is a check digit. The prefix tells you who owns the box, and the check digit tells you whether the number is valid.

This matters because you can be handed a substitute box at the depot. If the booking names one unit and a different unit arrives, the number is how you notice. The BIC owner code register lists the prefixes in use, and the check digit rule lets you test the number yourself.

Three checks on arrival take a minute each. Read the number against the booking. Look at the CSC plate, which records the safety approval and its expiry. Walk the inside for holes, roof damage and a smell that will transfer to your cargo.

The industry body for liner shipping publishes guidance on container condition and inspection. It is worth a read if you book often, not once. A box that passes a paper check can still fail a light test on the inside walls.

Photograph the number plate and the CSC plate before loading. If the cargo arrives damaged, those two photos answer the first question your insurer will ask.

Four Mistakes That Cost Real Money

The first is planning against the outside length. A 40ft box does not give you twelve metres of floor. The walls, the door frame and the corner posts take their share. Plan against the inside figure and leave a margin.

The second is buying a high cube for a load that will not pass the door. The cube is real, but it sits above the door line. If your crates are built tall and rigid, that space stays empty and you paid a premium for it.

The third is loading to the payload rating and forgetting the road. A box can be legally loaded by the shipping line and illegally loaded on the road. The fine lands on the truck operator, and the delay lands on you.

The fourth is mixing two products in one box without a loading plan. A partial load of heavy cargo at one end and light cargo at the other changes the weight distribution. A badly balanced box is refused or reworked at the gate.

Loading: Where the Plan Meets the Steel

A size decision made in an office meets reality at the loading bay, and that is where supervision earns its fee. A loading plan on paper says twenty pallets fit. A supervisor on site sees that two pallets are wrapped slightly wider and the last row will not close.

What a supervisor checks is narrow and useful. The count against the packing list. The weight distribution along the floor. Lashings and dunnage, so nothing moves at sea. Photographs of the load as it goes in, which is the only evidence that survives a dispute.

Floor strength is the quiet limit. A container floor is rated for a load spread across the deck, not for one heavy machine on four small feet. Point loading dents the deck and can put the box out of service, and the repair cost comes back to the shipper. Spread the weight on timber.

For cargo that fill the box by volume, the loading itself is the risk. A box loaded loose can lose a metre of usable length to settling. That is a whole pallet of cargo, and it is found too late.

Book the box by size, then supervise the loading as a separate step. The two decisions are made by different people, and mixing them is how a good plan becomes a short shipment.

The receiving rules add a layer above the box choice. Read the port and border side of a container shipment before you fix the size. The World Shipping Council also publishes background on how liner shipping handles container equipment.

Questions Buyers Ask About Container Size

The Bottom Line

Three sizes, one decision. The 20ft for dense cargo and small volumes. The 40ft for light cargo that fills a box. The high cube for cargo that are tall, not heavy.

Check the door before the volume. Check the road before the payload. Then photograph the number plate, because the box on the day is the box that matters, not the one in the brochure.