CBM vs Actual Container Capacity
CBM is useful for volume accounting, but it cannot prove how many rectangular cartons physically fit in a container. Geometry, orientation, doors and payload decide the usable count.
The CBM formula
For a rectangular carton in metres, CBM = length × width × height. A 0.6 × 0.4 × 0.3 m carton is 0.072 m³. Dividing a nominal 76.3 m³ container by 0.072 gives 1059 whole carton volumes. That calculation assumes the empty space can be subdivided arbitrarily, which real rigid cartons cannot do.
Why rectangular packing loses usable volume
A carton can leave strips of unusable width, length or height even when substantial cubic volume remains. Rotation may reduce those gaps, but the container is still a rectangular bin with a finite door and fixed dimensions. CBM therefore behaves like an upper-bound diagnostic rather than a guaranteed count.
Worked comparison
| Method | Result | What it considers |
|---|---|---|
| Nominal CBM division | 1059 carton volumes | Volume only |
| PackMize deterministic layout | 970 cartons | Internal geometry, rotations, door, payload, quantity |
| PackMize status | BEST SOLUTION FOUND | No unsupported global-optimum claim |
CBM is still useful
CBM remains useful for freight quoting, volume utilization and a fast impossibility check. If the total product volume already exceeds the available container volume, the shipment cannot fit geometrically. But if the volume test passes, a packing calculation is still needed to determine whether the rigid dimensions can actually be arranged.
Assumptions and data sources
PackMize separates published reference data from planning assumptions. Always replace a preset with the specification of the pallet, container, sheet or stock you will actually use when operational accuracy matters.
Frequently asked questions
Can CBM tell me the exact number of cartons?
Only in special cases where dimensions tile perfectly. In general CBM provides a volume-based upper bound, not a guaranteed physical arrangement.
Why can a container show free CBM when no more boxes fit?
The remaining space may be split into strips or voids that are individually too small for the next carton orientation.
Should I use nominal CBM or exact internal dimensions?
Use exact internal and door dimensions for operational planning. Nominal CBM is best treated as a descriptive volume figure.