How do you calculate how much mixed cargo fits in one container?

Mixed cargo cannot be calculated by dividing volumes. Every SKU has six possible orientations: two SKUs give 36 combinations and five SKUs give more than 7,000, which is impossible to work through by hand. The practical approach is a 3D loading tool — enter the dimensions, weights and quantity limits for every SKU and let the algorithm search length, width and height simultaneously, returning the quantity that fits and the loading rate.

Which cargo should be loaded first?

Three general rules: heavy cargo first and large items first, both at the far end of the container and on the floor; small items last, used specifically to fill the gaps between large items and the space above them. In zoned loading mode, the list order is the loading order — the first row goes in at the far end.

How do you plan cargo that cannot be stacked or must not be turned over?

For cargo that cannot take load, use no-stacking mixed loading: the algorithm places it on the floor only and puts nothing on top, while still using the side gaps beside it for other cargo. For cargo that must not be inverted, specify which face points up and lock that orientation before planning; the algorithm then searches for feasible arrangements within that constraint.

Does mixed cargo always load less than a single SKU?

Usually somewhat less, because different sizes interlock less neatly and create more gaps. But with good arrangement mixed loads still reach 80–90% loading efficiency, and small items are excellent gap fillers. By contrast, separating large and small items into two containers usually wastes more than mixing them.

How to Load Mixed Cargo in One Container: 3 Strategies Explained

Three or four different carton sizes in one container is the most everyday scenario in export and forwarding — and the hardest to calculate. This page explains why mixed loading is difficult, what each of the three loading strategies actually solves, and how to handle the real-world constraints that sit outside the algorithm: load-bearing limits, unloading sequence and do-not-invert cargo.

1. Why mixed cargo is harder than a single SKU

A single-SKU load is essentially an arithmetic question: container internal length 5,898 mm, carton 600 mm long, nine rows fit — one calculation and you're done.

Mixed cargo is different. Three difficulties compound:

Difficulty	What it means
Combinatorial explosion	Six orientations per SKU. Two SKUs = 36 combinations, three = 216, five = more than 7,700. Exhaustive manual work is impossible.
Fragmented space	Different sizes sitting together carve out many slivers "too small for anything". More fragments means lower loading efficiency.
Sequence sensitivity	What goes in first changes the outcome entirely. Loading small items early can block large items; saving them all for last may leave nowhere to put them.

So "how much mixed cargo fits" has no formula you can reach for. There are only two kinds of answer: "I'll estimate from experience", which is off by ten to several dozen cartons, or "let an algorithm work through all the SKUs together", which produces a specific, executable plan.
Setting the quantity limit to 0 means unlimited, in which case the algorithm simply tells you how many units this container can actually take — the most common question in mixed loading.

2. Three strategies and what each one solves

There is more than one way to load mixed cargo. Whether your cargo can bear weight on top and whether it has an unloading sequence determine which strategy to use. These are the three modes in the Container Loading Calculator — pick by your cargo conditions.

Strategy 1: Optimal mixed loading stack as high as the height allows

How it works: the algorithm fills the floor level first, then stacks upward where the floor is full, actively filling the gaps in front of, above and beside earlier cargo. After placing each group, it re-divides the remaining space for the cargo that follows.

Characteristics: the highest loading efficiency of the three. It squeezes every gap it can, at the cost of a more complex plan that must be loaded to the drawing.

Best for: cartons, cargo that can take stacked weight, loading efficiency as the priority, and no strict unloading sequence. This is the default mode to try first.

Strategy 2: No-stacking mixed loading fills side gaps · nothing on top

How it works: cargo is still placed group by group, but nothing is stacked on top of anything else. Floor space that one group cannot use is released for the next group to fill alongside.

Characteristics: loading efficiency is somewhat lower than optimal mixed loading, but every item sits on the floor or on its own layer, so nothing crushes anything else.

Best for: cargo that cannot take load — cartons that deform, precision components, liquid containers, glassware, and any order where the customer has stated "nothing on top".

Strategy 3: Zoned loading list order · far end to door

How it works: the container is divided into segments along its length in the order you list the cargo — the first row occupies the far end, the second row follows, and so on towards the door. Each segment fills its own space.

Characteristics: usually the lowest loading efficiency of the three (segments rarely fit together perfectly), but it delivers something valuable: a clear unloading sequence. Who comes out first is obvious at a glance.

Best for: multiple consignees, cargo unloaded in batches at different stops, or loading crews who need explicit zone instructions. The list runs top to bottom as the loading sequence, with the first row at the far end.

3. Choosing between the three modes

Your situation	Choose	Reason
Ordinary cartons, can be stacked and crushed	Optimal mixed	Highest efficiency — it consumes the volume
Fragile / precision / liquid cargo	No-stacking mixed	Nothing gets crushed, and side gaps are still used, so little is wasted
Multiple consignees / batch unloading	Zoned loading	Clear zones — unloading stays orderly with no need to dig through the container
You just need the "maximum that fits" number	Optimal mixed, quantity limit `0`	With no quantity limit it returns "how many units fit in this container"
A mix of crushable and non-crushable cargo	Start with no-stacking mixed	It is the safe baseline — confirm it all fits before optimising

4. Three real-world constraints outside the algorithm

These three strategies solve "does it fit geometrically". Real loading still involves three judgements that only a person can make:

1. Load-bearing capacity

How many kilograms the bottom of a carton can support, and how many layers before it collapses, is decided by the packaging — the algorithm has no way of knowing. If your outer cartons rely on board strength alone, restrict the number of layers deliberately (many calculators expose a "max stacking layers" parameter; 0 means unlimited).

2. Labour cost of loading and unloading

The algorithm's optimum sometimes means pushing small items into the deepest corner — two extra hours for the loading crew and worse for whoever unloads. Gaining 3% loading efficiency while doubling labour cost is a bad trade. Where there is an unloading sequence requirement, accept a few points lower efficiency and use zoned loading.

3. Cargo that must not be inverted

Some cargo may only sit one way up (equipment marked with "↑↑", packaging containing liquid). For these, lock the orientation before planning — otherwise the algorithm may lay them on their side to squeeze in more, producing a beautiful plan that simply cannot be executed.

⚠️ A detail that gets overlooked: a loading plan handed to a loading crew has to be readable. If you give them a dense list of 3D coordinates, they will load from experience instead — and the plan was pointless. A layered top view showing what goes in each row of each layer is worth more than a marginally better loading-rate number.

5. Frequently asked questions

How do I calculate how much mixed cargo fits in one container?: Not by dividing volumes. The workable method is to enter every SKU's dimensions, weight and quantity limit into a 3D loading tool and let the algorithm search all three axes. Set the quantity limit to 0 for unlimited and it returns how many units fit in the container.
Which cargo should be loaded first?: Three general rules: heavy cargo and large items first, at the far end of the container and on the floor; small items last, used to fill gaps and the space above. In zoned loading mode the list order is the loading order — the first row goes in at the far end.
Some cargo cannot be crushed and some cannot be turned over — how do I plan both together?: Use no-stacking mixed loading for the items that cannot take load; the algorithm puts nothing on top of them while still using the side gaps. For cargo that must not be inverted, specify which face points up first, lock the top face, then search for feasible arrangements under that constraint.
Does mixed cargo always load less than a single SKU?: Usually a little less, since different sizes interlock less neatly and leave more gaps. But arranged well, a mixed load still reaches 80–90% loading efficiency, and small items are exactly what fills gaps. Forcing large and small items into two separate containers "to make loading easier" usually wastes more.
Can a calculated plan go straight to the customer?: Yes. The calculator can print or export the loading plan, including a loading schedule, a 3D view and layered top views. Attaching one to a quotation is far more persuasive than saying "roughly this much should fit".

Enter several SKUs together and see how many units actually fit in one container

Open the Container Loading Calculator →