CBM & Ocean Container Loading Calculator
Calculate your cargo's CBM and how many 20ft, 40ft or 40ft High Cube containers it needs, using a realistic packing-efficiency factor.
1 container
Total cargo 6 m³ across 27.39 m³ usable per container (21.9% utilization).
| Metric | Value |
|---|---|
| Carton volume | 0.06 m³ |
| Total cargo volume | 6 m³ |
| Container internal volume | 33.2 m³ |
| Usable volume (after efficiency) | 27.39 m³ |
| Utilization | 21.9% |
Why nominal container capacity overstates what you can actually load
A 40ft container's advertised ~67.7 CBM interior is the volume of its empty steel shell — the number on a spec sheet, not a promise about how much cargo fits inside it. Rectangular cartons never tile a rectangular space with zero waste: door-swing clearance eats space at one end, load-bar fittings interrupt the side walls, and any deviation from a single uniform carton size opens up voids a bigger or smaller box can't fill. Treating nominal capacity as usable capacity is one of the most common freight-planning mistakes, and it's why experienced forwarders always apply a packing-efficiency discount before booking.
Choosing between 20ft, 40ft and 40ft High Cube
The choice usually comes down to whether your cargo is volume-constrained or weight-constrained. A 40ft High Cube offers meaningfully more usable volume than a standard 40ft for a similar rate in most trade lanes — a clear win for light, bulky freight that runs out of room long before it runs out of allowable weight. Dense, heavy cargo (metal parts, liquids, anything approaching a container's weight limit before its volume limit) gets no benefit from the extra height and should be sized on weight, not CBM, in the first place.
What this tool doesn't model
This is a loose-carton planning estimate, not a load plan — it assumes uniform carton dimensions and a single packing-efficiency percentage applied evenly across the whole container. Palletized freight, mixed carton sizes, and irregularly shaped cargo all pack less predictably than this model assumes; treat the output as a starting point for a conversation with your freight forwarder, not a number to book against without their sign-off.
How to use this calculator
- Enter one carton's dimensions and how many you're shipping.
- Choose a container size and packing efficiency.
- See total CBM and how many containers you need.
- Container internal volume
- Nominal internal (shell) capacity for a standard steel dry container. Real capacity varies slightly by manufacturer and container condition — always confirm against your carrier's spec sheet for booking-critical loads.
- Uniform carton size
- This tool assumes every carton is the same size. Mixed carton sizes typically pack less efficiently than a single uniform size at the same nominal packing-efficiency percentage.
Questions
Why can't I just divide the container's nominal capacity by my carton volume?
Because a container's printed capacity is its empty internal shell, and rectangular cartons never tile a rectangular box perfectly once you account for door-swing clearance, load-bar fittings, and any deviation from a single uniform carton size. Dividing straight by nominal capacity routinely overstates how many cartons will actually fit — that's exactly what the packing-efficiency input corrects for.
What packing efficiency should I actually use?
80–85% is a reasonable planning range for uniform, regularly-shaped cartons stacked by an experienced loading crew. Irregular shapes, mixed carton sizes, or palletized (rather than floor-loaded) cargo typically run lower — sometimes well under 70% — because pallets themselves waste vertical and horizontal space that loose cartons wouldn't.
Is a 40ft High Cube container really worth the extra cost over a standard 40ft?
It depends entirely on whether your cargo is volume-constrained or weight-constrained. A 40HC gives roughly 13% more usable volume than a standard 40ft for the same footprint and a similar rate in most trade lanes — a real win for light, bulky cargo that fills out on volume long before it hits a weight limit. For dense, heavy cargo that maxes out payload weight before it runs out of space, the extra height buys you nothing.
Does this tool account for pallets, or just loose cartons?
Loose cartons, packed directly — it doesn't model pallet footprints, stacking height limits, or the space a pallet's own structure wastes. If you're shipping palletized freight, treat this tool's output as an optimistic ceiling and apply a lower packing-efficiency percentage to compensate.
Sources
- How Many CBM in a Shipping Container? (20ft, 40ft & 40HC) — CBM Calculator (reviewed 2026-09-25)