How do you calculate container loading rate?

Loading rate = total loaded cargo volume ÷ nominal container capacity × 100%. For example, a 20GP has a capacity of 33.2 m³; loading 28 m³ of cargo gives a loading rate of 28 ÷ 33.2 ≈ 84.3%.

What is a good container loading rate?

For regular box-shaped cartons, 85–95% is a strong result. For irregular shapes, palletised cargo or mixed cargo of several sizes, 75–85% is normal and acceptable. Below 75% usually means the arrangement itself is suboptimal and there is clear room to improve.

Why do carton counts calculated from volume never fit in reality?

Dividing total volume by carton volume assumes the cargo fills the space perfectly. In reality the deciding factor is whether the dimensions divide evenly into the container. A container 5,898 mm long takes nine 600 mm rows and leaves 498 mm — not enough for a tenth row. The same waste occurs across width and height, and cumulatively it accounts for 10–20% less than the theoretical figure.

How do I improve the loading rate with mixed cargo sizes?

The core ideas are zoning and layering: keep cargo of similar size or height in the same zone so you do not waste the space above short stacks, and use smaller items to fill the gaps between large ones. Loading sequence matters too — large and heavy items go in first, at the far end and on the floor, with small items loaded last to fill gaps; otherwise you end up unable to get items through the door or leaving hollows inside.

How to Calculate Container Loading Rate (and 6 Reasons It Comes Out Low)

When a container load comes up short, the reason is almost never "the maths was wrong" — it's that only one arrangement was tried. This page gives the formula and the benchmark levels first, then takes apart the six real reasons a container ends up half empty, each with a fix you can apply immediately.

1. How to calculate the loading rate

Loading rate = total loaded cargo volume ÷ nominal container capacity × 100%

Example: a 20GP has a nominal capacity of 33.2 m³. Loading 28 m³ of cargo gives 28 ÷ 33.2 ≈ 84.3%.

Note what goes in the numerator: the outer volume of the cargo — not weight, and not net volume. Bulging cartons, packing tape and timber crating all count as cargo volume.

What counts as a good loading rate?

Loading rate	Level	Typical situation
Above 90%	Excellent	Single SKU, box-shaped cartons, dimensions that fit the container closely
85% – 90%	Good	Regular cargo with an optimised arrangement — solid performance
75% – 85%	Average	Mixed sizes, palletised cargo or irregular shapes
Below 75%	Low	Usually means the arrangement was not explored properly — clear room to improve

What does 10 percentage points of loading rate cost you?
Say a 40HQ costs $3,000 in ocean freight and the container holds 76.3 m³.
At 90% efficiency (68.7 m³) — about $43.7 per m³.
At 78% efficiency (59.5 m³) — about $50.4 per m³.
Same container, same money, $6.7 more per cubic metre — spread across every unit shipped. That is why the arrangement is worth calculating properly.

2. Six reasons a container isn't full — and what to do about each

Reason 1: Only one orientation was tried

A rectangular carton has six possible orientations (three pairs of opposite faces), and each one occupies different amounts of length, width and height. Most people instinctively try only "lying flat" — while the optimum may be a different face down.

Fix: make sure every SKU is tried in all six orientations. Once you have more than two sizes and dozens of pieces, exhaustive manual testing becomes impossible — which is exactly when a 3D loading algorithm should take over.

Reason 2: Dimensions don't divide evenly, so whole rows and columns get wasted

Container internal length 5,898 mm, carton 600 mm long: nine rows fit (5,400 mm) and 498 mm is left — not enough for a tenth row, so nearly half a metre goes to waste. The same problem applies across the width and up the height.

Fix: try to find the orientation that makes the remainder as small as possible in at least one dimension. As a rule of thumb, running the longest edge along the container length is usually better — but it is only a rule of thumb, so verify it rather than trusting it.

Reason 3: Mixing tall and short stacks leaves the top empty

Place 1.5 m tall cargo next to 0.8 m tall cargo in the same zone and the space above the short stack stays empty forever — and short stacks rarely support anything placed on top reliably.

Fix: group cargo by height and keep similar heights together; use the space above shorter stacks specifically for small items that can bear the load.

Reason 4: The loading sequence is wrong, so the best positions are taken too early

Loading proceeds from the far end back towards the door. If small items go in first, large items can no longer get in; if large items end up near the door, there is no room left for small items to fill gaps.

Fix: follow three sequencing rules — heavy cargo first, at the far end and on the floor; large items early, leaving access; small items last, used specifically to fill gaps. The layered top views produced by the calculator are ordered this way; load to the drawing and the sequence stays correct.

Reason 5: Weight hits the limit with half the space still free

Heavy cargo (density above the container's break-even point) reaches the payload ceiling at around 70% of the volume, and the remaining space cannot be used at all.

Fix: calculate cargo density first. Do not force heavy cargo into a high cube or a 45ft box — they offer more volume but no more payload, so they cost more per cubic metre. Heavy cargo belongs in a 20GP, or should be split across containers.

Reason 6: A single oversized item blocks a whole row

Any item wider than 2,340 mm or taller than 2,280 mm (2,585 mm for a high cube) cannot pass the door. Even one such item can make an entire row unloadable as planned.

Fix: screen the cargo list for door-limit violations before planning. Those items need to be disassembled, shipped in an open-top or flat-rack container, or taken out of the standard box entirely.

3. The order to improve loading rate in (cheapest first)

Step	Action	Why
1	Change the orientation	Costs nothing, changes nothing physical — pure gain from trying more arrangements. Biggest return, lowest cost.
2	Fix the loading sequence	Also needs no repacking, just getting the order of operations right.
3	Group and zone the cargo	Zone by height and load-bearing capacity, then use small items to fill the space above large ones.
4	Change the packaging dimensions	For example, trimming an outer carton from 60 cm to 58 cm to make the division work better. Requires supplier coordination; medium cost.
5	Change container type	Re-select the container by cargo density, or move the slight overflow into the next container. Affects quoting, but is often the most complete fix.

4. Why manual estimation gets it wrong

Three problems of different orders of magnitude stack on top of each other:

Orientation combinations: six orientations per SKU. Two SKUs give 36 combinations; five SKUs give more than 7,700.
Three-dimensional constraints: length, width and height are constrained simultaneously. Miss by a little in any one direction and overall capacity drops a whole tier.
Plus weight and the door: a perfect arrangement is worthless if it overloads the container or if an item cannot pass the door.

That is why the industry approach is: use a tool to produce feasible plans and loading rates, and use people to check the real-world constraints — packaging strength, whether items can be stacked, unloading sequence, and the de-stuffing conditions at the destination port. The tool answers "can it fit"; the person judges "is this sensible".

⚠️ Don't ignore the physical cost of loading and unloading. Sometimes the algorithm's optimum is achieved by pushing small items into the deepest corner — two extra hours for the loading crew and worse still at the receiving end. Gaining 3% loading rate while doubling handling cost is a bad trade. If your cargo has an unloading sequence requirement, choose a zoned plan that keeps access clear.

5. Frequently asked questions

What is a normal loading rate?: For regular rectangular cartons, 85–95% is a strong result. For irregular shapes, palletised cargo or mixed sizes, 75–85% is normal performance. Below 75% usually means there is still clear room for improvement.
Why do carton counts calculated from volume never fit?: Because dividing total volume assumes the cargo fills the space perfectly. In reality, the count is decided by whether the dimensions divide evenly. A container 5,898 mm long takes nine 600 mm rows and leaves 498 mm; the same waste occurs in every layer and every row, and cumulatively it comes to 10–20% below the theoretical figure.
How do I improve the loading rate with mixed cargo sizes?: Group and layer: keep cargo of similar size or height in the same zone to avoid wasting the space above short stacks, and use small items specifically to fill the gaps between large ones. Sequence matters too — large and heavy items first, at the far end and on the floor.
If the calculation says 95%, can that really be achieved?: In theory yes, provided the cargo is rigid and box-shaped, the dimensions suit the container, no space is needed for securing, and the cargo can be stacked to full height. Any soft packaging, pallet or unloading-sequence requirement pulls the real figure below the calculated one. Leave 5% of headroom when quoting a customer.
Is there a free tool that calculates this directly?: Yes. The Container Loading Calculator at the top of this page offers three modes — optimal mixed loading, no-stacking mixed loading and zoned loading — and returns the quantity that fits, loading rate, weight used and a loading plan, which you can print or export.

Try a different arrangement and see how much more fits — enter your dimensions to see the loading rate

Open the Container Loading Calculator →