This container loading calculator answers the question that decides an import order's cost: how much of this actually fits in one box? Enter the container's internal dimensions and payload, the size and weight of a carton or a loaded pallet, and the tool tests every legal orientation, reports the best one, and tells you whether the container fills on volume or on weight first.
Arb Digital maintains a free tools library covering the estimating maths that sits behind everyday commercial decisions, and this one exists because the difference between 79% and 92% container utilisation is real money on every shipment. The tool models a uniform load of identical units. It does not plan a mixed load, it does not sequence a stuffing order, and it is not a substitute for your forwarder's own load plan.
What This Container Loading Calculator Does
In carton mode it treats the container as a rectangular box and packs identical rectangular cartons into it in a simple block pattern. It tries all six ways of turning the carton — or only the two that keep the marked height vertical, if you set the upright rule — and reports whichever gives the highest count.
In pallet mode it fixes the pallet upright, works out how many pallet footprints fit the floor including the mixed pattern where some pallets are turned ninety degrees, and then multiplies by however many whole loaded pallet heights fit under the roof.
Either way, the supporting figures show the percentage of the internal volume used, the total loaded weight against the payload limit, the winning arrangement written out, and which of the two limits binds first.
The boundary with the neighbouring tool on the site is clean. The pallet calculator stops at the pallet: it works out how many cartons fit on a pallet footprint and how tall the stack becomes. This page starts where that finishes, taking either loose cartons or already-built pallets and fitting them to a shipping container. Use the two in sequence when your goods are palletised.
How to Use It
- Pick the container, then check the numbers. The presets load typical internal dimensions. Overwrite them with the figures on your carrier's specification — internals genuinely differ between builders.
- Choose cartons or pallets. Pallet mode keeps the unit upright and stacks whole layers; carton mode is free to rotate unless you say otherwise.
- Enter the unit's outside dimensions and weight. For a pallet, use the loaded footprint and the total height including the pallet itself, and the gross weight including the pallet.
- Set the orientation rule. If the cartons are marked this way up, or the goods cannot lie on their side, choose the upright option — it usually costs several percent of utilisation.
- Read the limiting factor. If weight binds first, a bigger container will not help; if volume binds first, better packing or a high cube will.
The Formula: Block Packing and Utilisation
For each orientation of the unit, the count along each container axis is the whole number of times the unit dimension divides into the container dimension:
units = floor(L ÷ l) × floor(W ÷ w) × floor(H ÷ h)
The floor function is what makes packing lossy. If a container is 235 cm wide and the carton is 30 cm wide, seven fit across and 25 cm is wasted — nearly 11% of the width, gone whatever you do. Utilisation is then the loaded volume as a fraction of the internal volume:
utilisation = (units × unit volume) ÷ (internal L × W × H)
Worked example. A 20ft container measuring 590 × 235 × 239 cm internally, loaded with 40 × 30 × 25 cm cartons. Standing the carton with its 40 cm side along the length: 14 fit lengthways, 7 across the width and 9 in height, giving 882 cartons. Rotating so the 25 cm side runs across the width gives 14 × 9 × 7 — the same 882. Putting the 30 cm side along the length gives 19 × 5 × 9 = 855, and the worst orientation gives 805. The winning load is 882 cartons at 0.03 m³ each, or 26.46 m³ inside a 33.14 m³ container: 79.8% utilisation. That figure is close to the practical ceiling for loose-loaded cartons, and it is why the last fifth of a container's volume is usually air.
Volume or Weight: Which One You Are Really Paying For
Every container has two ceilings, and dense goods hit the weight one long before the volume one. Loading the worked example above with 12 kg cartons gives 882 × 12 = 10,584 kg against a payload of roughly 28 tonnes, so volume binds and the extra payload capacity is wasted. Swap to 32 kg cartons and the weight limit stops you at about 880 cartons — the two limits arrive together. Anything heavier and the container ships part empty by volume.
This matters because it decides which fix works. If volume binds, better packing, flatter cartons, a high-cube container or removing packaging all help. If weight binds, none of them do: the only levers are lighter packaging, splitting the load across more containers, or a heavy-tested container where the route allows it.
Road legality is a separate ceiling that catches people out after the box is already stuffed. In the United States, federal limits on the Interstate system cap gross vehicle weight at 80,000 pounds with axle limits set by a bridge formula, and the FHWA commercial vehicle size and weight programme sets out how those apply. A container loaded to its marked payload can be perfectly legal at sea and illegal on the road at either end, because the tractor and chassis weight counts too. Check the road limit for the destination before you fill the box.
Where the Container Dimensions Come From
The outside of a shipping container is standardised. ISO 668, Series 1 freight containers — classification, dimensions and ratings, fixes the external length, width and height and the gross ratings for each type, which is what makes a container from any operator stack and lock onto any ship or chassis in the world.
The inside is not standardised in the same way. Wall thickness, corrugation depth, flooring and door hardware vary between builders, so two 40ft containers with identical external dimensions can differ by a few centimetres internally. A few centimetres is not academic here: it is exactly the amount that decides whether a seventh pallet row fits. That is why the presets on this page are editable and labelled as typical rather than authoritative, and why the number you should actually load is the one on your carrier's specification sheet for the container you have been allocated.
The other dimension worth checking separately is the door opening, which is smaller than the internal cross-section. A load that fits the interior can still be impossible to get through the doors, particularly with forklift-handled units that need clearance above the load.
Pallet Patterns and the Two-Block Trick
Pallets are where a few percent of utilisation is most easily won or lost, because the pallet footprint rarely divides neatly into the container width. Laid one way you might fit eleven pallets and waste a wide strip; turned ninety degrees you fit ten and waste a narrower one.
The standard answer is a mixed pattern. Fill part of the container's length with pallets in one orientation, then turn the remainder ninety degrees so the leftover strip becomes usable. The calculator tries every split point of that kind in pallet mode and reports the best combination it finds, which frequently beats either pure orientation by one or two positions per container.
Two practical caveats. Turned pallets are only loadable if the forklift can reach the fork entries in that orientation, and a mixed pattern leaves gaps that need dunnage or airbags to stop the load shifting at sea. Neither is a reason to avoid it, but both belong in the plan rather than being discovered at the loading bay.
Arb Digital's free tools library covers logistics, pricing and measurement maths for people running product businesses, and our team is happy to talk through anything the tools cannot answer.
Browse Free Tools Talk to Arb DigitalCommon Mistakes to Avoid
- Using external container dimensions — the walls, floor and roof structure take several centimetres off every axis. Only the internal figures pack anything.
- Dividing total volume by carton volume — that ignores the floor function and overstates the count by ten to twenty per cent. Cartons do not flow into corners.
- Forgetting the pallet in the pallet's dimensions — the footprint and height must include the pallet itself, and the weight must include it too.
- Ignoring the road weight limit — a legally loaded container can be an illegally loaded truck once the tractor and chassis are added at either end.
- Assuming every 40ft container is the same inside — internal dimensions vary by builder, and a few centimetres decides whether an extra row fits.
Related Free Tools From Arb Digital
Use the pallet calculator to build the pallet before you load it, the freight class calculator when a domestic shipment needs a density-based class, the density calculator to check whether goods will bind on weight or volume, the shipping cost per item calculator to turn a container rate into a unit landed cost, and the luggage linear inches calculator for the same fit-it-in-the-box question at travel scale. Everything else is in the free online tools hub.
Frequently Asked Questions
It depends entirely on carton size. A 40 by 30 by 25 cm carton fits 882 times in a 590 by 235 by 239 cm interior, using about 80 per cent of the volume. Change any dimension by a few centimetres and the count can move by dozens.
Because cartons cannot be cut. Each axis fits only a whole number of units and the remainder is wasted air, so volume division typically overstates the real count by ten to twenty per cent.
Around 75 to 85 per cent is normal for loose-loaded uniform cartons, and palletised loads are usually lower because the pallet itself takes height and the footprints leave gaps. Above 90 per cent generally means the carton size was chosen to suit the container.
Only if volume is the binding limit. A high cube adds about 30 cm of internal height, which helps light bulky goods and does nothing at all for a load that already hits the payload ceiling.
No, they are typical values you should overwrite. ISO 668 standardises the external dimensions and ratings, but internal dimensions vary between builders, so use your carrier's specification for the container you have been allocated.
No. The door opening is smaller than the internal cross-section, so check it separately, especially for tall pallets or anything handled by forklift that needs clearance above the load.
A pallet calculator works out how cartons sit on one pallet footprint. This tool takes the finished pallets, or loose cartons, and fits them into a shipping container, including the mixed floor patterns that pallets often need.
This tool estimates a uniform block load from the dimensions you enter. It is not a stowage plan, does not assess weight distribution, securing or dangerous goods, and does not replace the load plan agreed with your carrier or freight forwarder.
