What container dimensions does the calculator use?

ISO 668:2020 internal dimensions: 20GP is 5,898 x 2,352 x 2,393 mm with payload around 28,000 kg, 40GP is 12,032 x 2,352 x 2,393 mm around 26,500 kg payload, 40HC is the same length and width but 2,696 mm internal height. Real carrier limits run a few hundred kilograms below the ISO max because of tare variance and road-legal limits at origin and destination.

Why does the result say weight-out at 65 percent cube?

For dense cargo (steel drums of liquid, IBCs of resin, big bags of inorganic salts), the container reaches its payload limit well before its volume limit. The result panel shows the binding axis so you can decide whether to upgrade to a heavier container build, switch packaging to a lighter format, or simply accept the unfilled volume rather than pay deadweight on the freight.

Does the math account for pallet headers and dunnage?

Yes, where the packaging format has a typical pallet footprint and stack height the calculator uses those numbers. It does not account for dunnage bags, edge protectors, or special bracing for liquid drums on rough seas; ask the forwarder for the loading pattern that they will actually use, especially for high-vibration lanes such as a US West Coast all-water service in winter.

How is the 25 kg paper bag pallet count calculated?

A standard 1,200 x 1,000 mm euro pallet stacked 5 layers x 8 bags = 40 bags = 1,000 kg, or 1,200 x 800 mm shipped at 5 x 7 = 35 bags. The exact number depends on the bag dimensions and the supplier stacking pattern. The calculator uses the most common 25 kg pattern for the chemical-export trade; ask the supplier for the actual bag dimensions to refine the count.

Does the tool cover reefer or special equipment?

The dataset includes 20-foot and 40-foot reefer (refrigerated) containers with reduced internal cube. Flat-rack, open-top, and tank container builds are not in the dataset; for those, work with the iso-tank-loading calculator at /tools/iso-tank-loading or the ISO tank type reference at /iso-tanks.

ISO 668 · Capacity Math

Container Loading Calculator

Compute how many drums, IBCs, big bags, or paper-bag pallets fit a 20'GP, 40'GP, 40'HC, or reefer container.

Container

Cargo packaging

Calculator method (so you can verify by hand)

Units per tier: floor(internal length ÷ unit footprint length) × floor(internal width ÷ unit footprint width).
Tier count: the lesser of (internal height ÷ unit height) and the packaging's stack rating.
Volume cap: units capped at floor(internal volume × 0.95 ÷ unit volume) to allow for void space.
Weight cap: floor(container max payload ÷ (unit net mass + tare)).
Loading result: the lower of the volume cap and the weight cap. The lower of the two is the limiting factor.

For a deeper breakdown of cargo packaging see the glossary entries: 20-foot container, 40-foot container, 40-foot high cube, reefer container, drum, IBC, big bag, and ISO tank.

A worked example

The booking. You quote a 40HC of bagged citric acid and size it on volume: the cartons cube out the box, so you commit to the full container load on the quote.

The failure. It weighs out first. The bagged cargo grosses past the 40HC payload cap well before the cartons fill the floor and roof, so the container is rejected at the terminal for overweight, or you ship it part-full and pay for air. Cube was the wrong binding dimension; weight was.

The fix. Run both constraints here before you quote. The calculator returns the load by floor and height and by payload, and names which one binds. Quote against the binding dimension and the box loads to its real capacity with no overweight reject.

For drummed or IBC cargo specifically, the drum and IBC palletising calculator is at /tools/chemicals/drum-ibc-palletising-calculator, and every box's internal dimensions and payload sit in the container types reference.

Bulk liquid in an ISO tank?

ISO tank loading uses different math: thermal-expansion fill cap, hard ceiling 95% or 97% by hazard class, the 20% to 80% surge floor, plus MAWP and lining-compatibility checks. That calculator lives on its own page.

Open the ISO Tank Loading Calculator