Shipping Container Dimensions — 20ft, 40ft & 40ft High Cube Specs

Every container-fit decision starts with the same three ISO dry boxes. The table below shows internal dimensions, realistic usable volume, and legal payload — the numbers the QuickCBM calculator uses for its cross-check.

Why usable volume is less than geometric volume

Multiply the internal dimensions of a 40ft container and you get about 67.7 m³ of geometric space — yet experienced loaders plan for 55–65 CBM. The difference comes from carton geometry (boxes rarely tile the space perfectly), door clearance, dunnage and airbags, and the practical limits of hand-stacking. Planning to 90–95% of theoretical capacity is the industry norm; planning to 100% is how cargo gets crushed.

A note on weight

Notice that a 20ft container legally carries more weight than a 40ft. Maximum gross mass is the same (30,480 kg) for both, and the 40ft box itself is heavier, leaving less for cargo. Dense products like tiles, stone or fasteners often max out a 20ft’s payload at half its volume — which is why the calculator checks volume and weight independently. See weight limits & VGM for the legal side.

Other equipment you may be offered

45ft High Cube (~86 CBM) exists on some trade lanes for very light cargo. Reefers (refrigerated) sacrifice roughly 10–15% of internal volume to insulation and machinery. Open top and flat rack equipment serve out-of-gauge cargo and are priced case by case. For standard cartonised goods, the three dry boxes above cover practically every shipment.

Door apertures matter for large items

The door opening is smaller than the internal cross-section — roughly 2.34 m wide and 2.28 m high on standard boxes (about 2.58 m high on High Cubes). A crate that fits the internal height on paper may not pass through the doors. The calculator’s dimension check compares your carton against internal walls; for single oversized crates, always check the door aperture too.

Payload vs volume: which limit hits first?

Every container has two independent ceilings — how much space it holds and how much weight it can legally carry — and which one you hit first determines your whole loading strategy. The rule of thumb loaders use is the break-even density of roughly 400–430 kg/CBM for a 40ft container. Cargo denser than that fills the weight limit before the space; cargo lighter than that fills the space first.

Concretely: a 40ft standard holds about 65 usable CBM and 26,680 kg of payload. Divide and you get ~410 kg per CBM. Ship anything heavier than that on average — tiles, stone, tinned food, liquids, machinery — and you will run out of kilograms with the container half empty. Ship anything lighter — furniture, textiles, plastics, packaging — and you will run out of cubic metres with tonnes of payload to spare. The calculator shows both numbers side by side precisely so you can see which ceiling binds.

The 20ft weight advantage explained

A common surprise for new importers: a 20ft container can legally carry more cargo weight than a 40ft. Both have the same maximum gross mass (30,480 kg under most ISO ratings), but the 40ft box weighs about 3,750 kg empty versus 2,300 kg for the 20ft. That leaves the 20ft with roughly 28,180 kg of payload against the 40ft’s 26,680 kg. For dense cargo, two 20ft containers can therefore carry more total weight than a single 40ft, even though they offer far less volume. This is why heavy commodities frequently ship in 20ft equipment.

High Cube: when the extra 30 cm pays for itself

The 40ft High Cube adds 30 cm of internal height (2.69 m vs 2.39 m), lifting usable volume from ~65 to ~68 CBM. For light, bulky cargo that is weight-unconstrained, that is a free 4–5% more product per shipment at a marginal freight premium — often the single easiest way to lower freight cost per unit. For dense cargo that hits the weight limit anyway, the extra height is wasted, since you cannot fill it without exceeding payload. Choose the High Cube by cargo density, not by habit.

Door apertures and loading clearance

Internal dimensions are not loading dimensions. The door aperture of a standard container is about 2.34 m wide and 2.28 m high — narrower and lower than the internal cross-section. A crate that fits the internal height on a spreadsheet can be physically impossible to get through the doors. Add to that the practical need for bracing, dunnage and airbags to stop cargo shifting in transit, and the reason experienced loaders plan to 90–95% of theoretical volume becomes obvious. Planning to 100% is how cargo arrives crushed.

Reefers, open tops and flat racks

Standard dry boxes cover the vast majority of cartonised freight, but three specialist types come up often enough to know. Reefers (refrigerated) sacrifice 10–15% of internal volume to insulation and machinery, so a 40ft reefer offers closer to 59 CBM. Open tops take cargo loaded by crane from above — tall machinery that will not fit through doors. Flat racks handle out-of-gauge loads that overhang a normal container. All three are priced case by case and booked well in advance.