A consolidated shipment of six SKUs from three suppliers sounds efficient. It usually ships at 65-70% volume utilisation, and the missing third is not a rounding error — it is paid freight.

The calculation, plainly 

volume_utilisation = sum(carton_volume × carton_count) / container_usable_volume

Usable volume is not the nominal container figure. A 40HQ is quoted at 76 m³; usable after pallets, dunnage and the fact that cartons do not tessellate perfectly is closer to 62-66 m³ for mixed cartons.

If your six SKUs total 44 m³ of carton volume, you are paying for 62 m³ of ship.

The three reasons it empties out

Carton dimension churn. Supplier A ships 60×40×35 and Supplier B ships 58×38×34 for a similar product. Four percent per axis is eighteen percent per carton in volume terms, and the pallet pattern changes with it.

Single-SKU pallets. Each supplier palletises its own SKUs. Six partial pallets occupy the footprint of six pallets, and the vertical space above each stack stays empty. Mixed pallets fix this and require a warehouse step most small importers do not have.

Last-minute quantity drops. One SKU gets cut after the booking is made. The container is not re-optimised; it just ships lighter while the freight stays the same.

What actually helps

Modelling the load before the booking, with real carton dimensions rather than an assumed size. We keep a small script that takes carton counts and dimensions and reports the best pallet pattern and the resulting utilisation — it takes ten minutes and routinely finds 8-12 percentage points.

The other lever is choosing the mode deliberately rather than by habit. Small consolidated orders often lose less money on air than on a partially filled sea container once the empty volume is priced in, which is the comparison we walk through in sea freight versus air freight for toys.

The MOQ interaction

Volume utilisation and MOQ pull against each other. Rounding an order up to hit a supplier's MOQ fills the container and improves utilisation, but it also buys inventory you may not sell. Rounding down fills nothing.

The useful framing is: utilisation is a cost per unit question, not a percentage to maximise. We covered the quantity side in the wholesale MOQ guide.

Bottom line

If a consolidated shipment comes in under 75% volume utilisation and nobody modelled it in advance, the freight line was a guess. Thirty percent empty is the default outcome, not bad luck.