Weighing out versus cubing out

Every container has two limits: how much space is inside it, and how much weight it is allowed to carry. Your products will hit one before the other. Which one they hit decides your freight cost per unit, and getting it wrong is the most common costing error in FMCG import.

The two limits

A standard 20-foot general purpose container offers roughly 33 cubic metres of internal volume and a payload limit in the region of 28 tonnes, though the road legal limit at destination is frequently lower than what the box itself can carry.

A 40-foot high cube offers roughly 76 cubic metres against a payload broadly similar to the 20-foot, perhaps a little more. That asymmetry is the important part: a 40-foot high cube gives you more than double the volume for roughly the same weight allowance.

That single fact determines which box you should be shipping in.

Which products do what

Goods that weigh out fill the weight allowance while the container still has space:

• Sugar in 50 kg bags
• Rice
• Detergent powder
• Canned food
• Bottled liquids in larger formats

For these, a 20-foot container is usually correct. Paying for a 40-foot gets you space you cannot legally fill.

Goods that cube out fill the space while the container is still light:

• Toilet tissue and paper products
• Biscuits and snacks
• Empty packaging
• Sachets and lightweight personal care

For these, a 40-foot high cube is almost always correct, because volume is what you are buying.

Working it out

Take carton volume in cubic metres, carton gross weight in kilograms, and divide.

Volume-limited quantity = usable container volume ÷ carton volume Weight-limited quantity = payload limit ÷ carton gross weight

The lower number is your answer, and it tells you which constraint binds.

Use about 86 per cent of nominal volume. You cannot stack to the ceiling in every part of the box, cartons do not tessellate perfectly, and pallets consume height and floor space.

A worked example. Cartons of 400 g tomato paste at 0.015 m³ and 10.5 kg gross.

By volume, into a 20-foot at 30 usable cubic metres: 30 ÷ 0.015 = 2,000 cartons. By weight, at 26 tonnes usable payload: 26,000 ÷ 10.5 = 2,476 cartons.

Volume is lower, so this cubes out at roughly 2,000 cartons and the container goes out around 21 tonnes, comfortably inside the weight limit. Moving to a 40-foot high cube roughly doubles the cartons and stays inside the weight allowance, which makes the 40-foot the better freight economics per unit.

Now the same exercise for 50 kg sugar bags at 0.0585 m³ and 50.5 kg.

By volume: 30 ÷ 0.0585 = 513 bags. By weight: 26,000 ÷ 50.5 = 515 bags.

These come out almost identical, which is why sugar in 50 kg bags is close to a perfectly matched load for a 20-foot container. A 40-foot would give you volume you cannot use.

Palletised versus floor-loaded

Palletising costs you about 12 per cent of usable volume. The pallet itself takes height and the footprint rarely matches the container width exactly. In exchange you get faster loading and discharge, less handling damage, and in some destinations a materially lower discharge cost.

Floor-loading maximises the fill but takes longer at both ends and handles the cartons more. For a buyer with mechanised handling at destination, pallets usually win despite the volume loss. For a buyer discharging by hand into a wholesale market, floor-loading usually wins.

Mixed containers

Combining a dense line with a light one lets you approach both limits at once, which is the most freight-efficient thing you can do.

Detergent powder plus toilet tissue is the classic pairing. The powder brings the weight, the tissue fills the space, and the two together get closer to a full box on both axes than either alone.

The constraint is compatibility. Some things must not travel together regardless of how well the numbers work: tea, coffee and spices absorb odour from soap, detergent and perfumed products and will be ruined. We will not consolidate those combinations even if asked.

What is published on this site

Every pack row on every specification page publishes carton dimensions, cubic volume, gross and net weight, cartons per pallet, and cartons per 20-foot GP, 40-foot GP and 40-foot high cube. Those figures are the maximum that physically load.

If you are mixing products, send us the combination and we will confirm the fill before quoting.