How Many CBM Fit in a 20ft Container? Capacity Chart for 20GP, 40GP, 40HQ and 45HQ

A 20ft general purpose container has a nominal capacity of 33.2 m³ (1,172 cu ft), but most real loads come in at 28–31 m³ (990–1,095 cu ft). That gap isn't a calculation error — cartons never sit perfectly tight, the door opening is narrower than the box, and no cargo shape fills a space exactly. This page puts nominal capacity, realistic loadable volume and weight limits for the four most common container types side by side, and shows when your shipment is limited by volume and when it's limited by weight.

1. Capacity and realistic loadable volume

Imperial quick reference

Note: figures above are industry-standard reference values. Boxes from different manufacturers and different production batches vary by a few centimetres, so always use the carrier's published data when booking. Realistic load is estimated at 85–95% loading efficiency — the more regular and box-shaped your cargo is, the closer you get to the top of that range.

2. Five reasons those 33.2 m³ never get filled

1. The door opening is narrower than the box, and the walls aren't flat

A 20GP has a clear door width of about 2,340 mm while the widest point inside is 2,352 mm. Twelve millimetres sounds trivial, but it decides whether an oversized item can go in at all. On top of that, corrugated reinforcement ribs run along both side walls, so usable width is often a little narrower than the nominal figure.

2. Cartons never sit perfectly tight

Cartons are soft. Bulging sides, folded flaps and the thickness of packing tape all turn "a perfect fit" into "a centimetre or two short". Over a 12-metre container, one centimetre per row multiplied by dozens of rows adds up to several cubic metres.

3. Cargo dimensions rarely divide evenly into container dimensions

Say the internal length is 5,898 mm and your carton is 600 mm long: you fit 9 rows (5,400 mm) and 498 mm is left over — not enough for a tenth row. Half a metre wasted. Rotate the carton and you may gain a whole extra row. This is exactly why 3D loading needs an algorithm rather than mental arithmetic.

4. You have to leave room for securing and cushioning

In real loading, space is left at the door and along the sides for air bags or timber bracing to stop cargo shifting in transit. That space is mandatory and cannot be counted as loadable volume.

5. Sometimes weight hits the limit first

With dense cargo, the container reaches its weight limit while it's still only 70% full by volume — and no amount of leftover space helps. The next section covers this case.

3. Volume-limited or weight-limited? It comes down to density

The same 20GP can take 33 m³ of cotton and as little as 5 m³ of steel plate. What decides it is cargo density — kilograms per cubic metre. Every container type has a break-even density:

4. Worked example: 60 × 40 × 50 cm cartons in a 20GP

So the answer for this cargo in a 20GP is roughly 248 cartons. But note that this assumes 90% efficiency: how many actually fit depends on how the cartons are arranged. The same 248 cartons may not fit at all with one layout, or another layout may squeeze in a dozen more. That's precisely where 3D calculation earns its keep.

5. Frequently asked questions

How much weight can a 20ft container carry?

A 20GP weighs about 2.2 tonnes empty with a typical maximum gross weight of 30.48 tonnes, so the payload ceiling is around 28 tonnes. However, carriers apply lower limits depending on the trade lane and season (Europe and North America especially). Confirm the figure with the shipping line before planning the load — never plan against the theoretical number.

How much more does a 40HQ hold than a 40GP?

The floor area is identical (12.03 m × 2.35 m); only the height differs. Internal height is 2.393 m in a 40GP versus 2.698 m in a 40HQ — about 30 cm more, which converts to 8.6 m³ or roughly 12.7% extra volume. If your cargo can be stacked, the 40HQ is almost always the better choice.

How much cargo fits when goods are palletised?

The pallet adds height (typically around 15 cm) and pallets rarely sit flush against each other, so loading efficiency falls from 85–95% to 70–85%. For palletised cargo in a 20GP, 23–28 m³ is a safe planning figure.

Is a 45HQ always the best value?

No. 45ft containers are less common, are restricted in inland transport (many countries and inland points do not accept them), and their payload ceiling is actually slightly lower than a 40GP. Their advantage only shows with genuinely light cargo — below 320 kg/m³.

How do I work out how much my own cargo will fit?

Use the Container Loading Calculator at the top of this page: enter the container type plus each carton's dimensions, quantity and weight, and it calculates how many units fit, the loading efficiency, the weight used, and draws a loading plan. Free, no installation required.