How many CBM fit in a 20ft, 40ft, or 40ft high cube container? The short answer:
| Container | Nominal capacity | Practical carton load |
|---|---|---|
| 20ft Dry (20DC) | 33.2 m³ | ~25–28 CBM |
| 40ft Dry (40DC) | 67.7 m³ | ~54–58 CBM |
| 40ft High Cube (40HC) | 76.3 m³ | ~60–68 CBM |
The longer answer is about the gap between those two columns — because quoting a customer or sizing an order against the nominal figure is one of the most common and expensive planning mistakes in ocean freight.
Nominal Capacity: The Geometry Ceiling
Nominal capacity is simply internal length × width × height (full specs on the container dimensions guide). Those internal dimensions derive from the ISO 668 container standard, which is why nominal capacities are consistent across carriers. You will never load 67.7 CBM of cartons into a 40DC: cartons are rigid rectangles, and unless their dimensions divide evenly into the container's in every axis, you lose slices of space along the walls, under the ceiling, and at the door end.
What Actually Determines Practical Capacity
1. Carton dimensions relative to the container. The dominant factor. A 60 × 40 × 40 cm carton loads a 40DC to about 71% (48 CBM) with orientation optimization; a slightly different carton can reach 80%+ in the same box purely because it tessellates better. There is no formula shortcut — it's a packing computation. The container loading calculator runs the actual arrangement in your browser and shows the fit in 3D.
2. Rotation constraints. "This side up" cargo cannot use its height as depth. Locking rotation typically costs 3–10 percentage points of utilization.
3. Palletized vs floor-loaded. Pallets add their own footprint and height and rarely tile the floor perfectly. Palletized loads usually land at 50–60% volume utilization; floor-loaded cartons reach 70–85%. That difference — roughly 10+ CBM in a 40ft — is why high-volume, low-value cargo often ships floor-loaded despite the handling cost. See how many pallets fit in a container.
4. The weight ceiling. A 40DC's payload is ~28,800 kg; a 20DC's is ~28,200 kg. Dense cargo (tiles, hardware, canned goods) hits the weight limit long before the volume limit — a 20DC "fills up" at 28.2 tons even if two-thirds of the space is empty air. More in container weight limits and VGM — the VGM (verified gross mass) declaration itself is a SOLAS requirement administered by the IMO, and it applies to every packed container regardless of how full it is.
Rules of Thumb by Cargo Profile
| Cargo profile | 20DC | 40DC | 40HC |
|---|---|---|---|
| Uniform cartons, rotation allowed | 26–28 CBM | 55–58 | 63–68 |
| Uniform cartons, this-side-up | 24–26 | 52–55 | 58–63 |
| Palletized (EUR/GMA) | 18–22 | 38–45 | 42–50 |
| Mixed carton sizes (manual load) | 22–25 | 48–54 | 54–60 |
These are planning benchmarks, not promises — run your actual carton size before booking.
How Many CBM Fit in Practice: A Shenzhen Consolidation Example
An FBA seller consolidating a season's stock in Shenzhen has 1,200 cartons of 50 × 35 × 30 cm at 7 kg each: 0.0525 CBM per carton, 63 CBM and 8,400 kg in total. Read against the nominal column, a 40DC (67.7 m³) looks like a comfortable fit. Read against the practical column, it is not: a this-side-up carton load in a 40DC realistically stows 52–55 CBM, and even with free rotation the benchmark tops out around 58. The shipment belongs in a 40HC, whose 60–68 CBM practical range covers 63 — but near the top of a range is exactly where you stop trusting benchmarks and compute the actual stow. Open this exact load in the container loading calculator to see the 3D arrangement, or run max-fill mode to see how many of these cartons the 40HC takes at most.
Now the cost consequence of getting it wrong. Had the seller booked the 40DC on the nominal figure, roughly 5–10 CBM of cartons would have been shut out at the origin warehouse. The leftover typically ships as a separate LCL consignment — billed per revenue ton, with its own origin charges, documentation and destination handling, and often arriving on a different vessel and a different customs entry. On most lanes that overflow shipment alone costs more than the entire rate premium of stepping up to a 40HC would have. The nominal-vs-practical gap is not an academic distinction; it is the difference between one clean container and a container plus an expensive orphan shipment.
Common Capacity Mistakes and What They Cost
- Quoting customers on nominal volume. A trader who promises "67 CBM per 40ft" to a buyer has committed to roughly 10 CBM that will not physically load. The shortfall either ships at the trader's expense or becomes a contract dispute.
- Ignoring the payload ceiling on dense cargo. Ceramic tile at around 2,000 kg/m³ maxes out a 40DC's 28,800 kg payload at roughly 14–15 CBM — about a fifth of the nominal volume. Booking space by CBM for dense cargo overbuys volume and can even trigger overweight penalties at the terminal or on the road leg.
- Forgetting the door aperture. The door opening is lower than the internal ceiling — about 228 cm high on a standard-height box and 257.7 cm on a 40HC. A pallet stacked to clear the 239.3 cm interior will still not pass through the doors; pallet height plans have to work from the door figure, not the ceiling.
- Counting pallet CBM instead of carton CBM. A packing list that sums loaded-pallet volumes double-counts the air between cartons and pallet edges. Capacity planning needs the carton CBM; the pallet CBM only matters for LCL billing and warehouse storage.
Most of these are avoidable with better load design rather than a bigger box — how to maximize container space covers the orientation, carton-size and floor-vs-pallet decisions that add real CBM without adding freight spend.
Edge Cases Worth Knowing
- 45ft High Cube. On some lanes a 45HC (86.1 m³ nominal) is available for cargo that outgrows a 40HC; availability and pricing vary far more than for the standard three sizes.
- Overheight and overlength pieces. Cargo that cannot pass the door aperture moves in open-top or flat-rack equipment, where "CBM capacity" stops being the constraint and lashing, gauge and crane access take over.
- Dunnage eats volume. Airbags, edge protectors and desiccant take a small but real slice of the stow — typically a percent or two — which matters exactly when a load is computed to fit near the top of a practical range.
When to Step Up a Container Size
- Above ~26 CBM of real cargo — a 20DC is at risk; price a 40DC.
- Above ~56 CBM — price a 40HC: it typically costs only a small premium over a 40DC while adding ~8.6 m³ of nominal space.
- Above ~66 CBM — two containers, or revisit carton design.
And below roughly 13–15 CBM, FCL may not be worth it at all — see FCL vs LCL for the break-even math.
How many CBM fit in a 40ft container?
Nominally 67.7 m³, but with real cartons expect 54–58 CBM (floor-loaded) or 38–45 CBM (palletized).
How many CBM fit in a 20ft container?
Nominally 33.2 m³; practically 25–28 CBM for floor-loaded cartons.
Why can't I use the full nominal volume?
Cartons don't tessellate perfectly into the container's internal dimensions, and rotation limits, pallets, and the payload weight ceiling all remove usable space.
Is a 40HC worth it over a 40DC?
Usually yes for light, bulky cargo: about 8.6 m³ more nominal volume for a small rate premium. For dense cargo that hits the weight limit first, the extra height buys nothing.
How many cartons fit in a 20ft container?
It depends entirely on carton size. At 60 × 40 × 40 cm (0.096 CBM each), a floor-loaded 20ft typically takes roughly 260–290 cartons — the 25–28 CBM practical range of its 33.2 m³ nominal volume.
Does a 40ft container hold twice as much as a 20ft?
By volume, slightly more than twice: 67.7 m³ vs 33.2 m³. By weight, no — payloads are nearly identical (28,800 kg vs 28,200 kg), so dense cargo that maxes out weight gains almost nothing from the bigger box.