Layer patterns: how cartons are arranged on a pallet

Why the pattern matters more than the carton size

Two pallets loaded with identical cartons can differ by a whole carton per layer – purely because of the arrangement. Over eight layers that’s eight cartons per pallet; over an order, it can be an entire pallet. The pattern also decides whether the stack holds together in transit and how much load the bottom cartons carry.

Three questions guide the choice:

1. Area: how many cartons fit in one layer?
2. Interlock: do the layers hold one another, or do separate columns stand loosely side by side?
3. Compression strength: do carton edges sit on carton edges, so the walls carry the load?

The basic calculation – cartons per layer × layers – is covered in How many cartons fit on a Euro pallet?

Grid (column stacking)

Every carton in a layer faces the same way and each layer sits exactly on top of the last. The result is a set of vertical columns.

• Strength: corners and walls line up exactly, so the cartons’ compression strength is used in full – which matters for tall stacks and long storage.
• Weakness: the columns aren’t tied together. Without stretch film or strapping they can drift apart.
• Area: only optimal when the carton divides the pallet evenly. A 400 × 300 mm carton on 1,200 × 800 mm gives 4 × 2 = 8 and covers the deck completely.

Interlock: bridging the joints

In an interlocked stack every other layer is arranged differently, so cartons bridge the joints of the layer below – much like bricks in a wall. The stack becomes stiffer as a whole.

• Strength: better load stability, especially with small, light cartons.
• Weakness: some carton edges rest on lids rather than on edges. Usable compression strength drops, which is a real risk for heavy stacks.

Interlocking often costs area. A 400 × 300 mm carton fills a Euro pallet with 8 in only one way: every line across the 800 mm width must meet exactly two 400 mm edges, because 800 can’t be made up of 300 mm pieces. Any layer that offsets the joints therefore holds fewer cartons – 7, for example: three lengthwise in one 300 mm row, four crosswise in the remaining depth.

Two-block: two grids side by side

The pallet is split into two areas with the cartons oriented differently in each. It’s the simplest way to use the leftover strip a plain grid leaves empty.

Example: industrial pallet 1,200 × 1,000 mm, carton 400 × 300 mm. A grid manages 9 (3 × 3). Split the 1,000 mm into a 400 mm strip and a 600 mm strip: the first takes 4 cartons crosswise, the second 2 × 3 = 6 lengthwise – 10 cartons, and the deck is fully covered.

Because the two blocks face different ways, a two-block pattern also adds a little interlock within the layer.

Pinwheel

Four identical blocks sit in a ring around the centre, each turned 90° from its neighbour, like the sails of a windmill. The pattern locks into itself and suits square or nearly square load areas.

The geometry is simple: with blocks measuring a × b you get a square with side a + b and a gap of (a − b) × (a − b) in the middle. Two 400 × 300 mm cartons side by side make a 600 × 400 mm block; four such blocks form a 1,000 × 1,000 mm square holding 8 cartons around a 200 × 200 mm gap.

The central gap is the price you pay. With soft or heavy cartons it can let upper layers sag.

Five-block: a pinwheel with the centre filled

A five-block pattern adds a fifth block in the middle of the four outer ones, putting the pinwheel’s gap to use when it’s big enough.

Example from JetPallet’s reference projects: 400 × 300 mm cartons on a 1,100 × 1,100 mm pallet. A grid gives 6 per layer, a two-block pattern 8, and the five-block 9. Over four layers that’s 36 cartons instead of 32.

Five-block patterns are hard to find by hand. The number of possible splits grows quickly, which is where a systematic search pays off.

Layer sequence: repeated, rotated 180° or mirrored

Even with the same pattern, not every layer has to sit the same way. Three sequences are common:

That last point is critical: a rotated or mirrored pattern can leave cartons only partly supported by the layer below. An example shows it: 800 × 800 mm cartons on a 1,000 × 800 mm load area with the second layer mirrored – the top layer has just 75% support. JetPallet therefore checks the geometric support of every layer transition. Full support is the default; a minimum between 0.1 and 100% can be set. This is a geometric check, not proof of stability.

Column/interlock hybrid: the two can be combined. In JetPallet you can stack the bottom layers in register as columns – where the load is highest and compression strength matters most – and alternate the layers above according to the chosen sequence. You decide how many bottom layers stay in columns; the support check applies to every layer transition.

Overhang and underhang

The pattern doesn’t have to stop exactly at the pallet edge.

• Overhang: the load sticks out beyond the pallet, which can make room for more cartons. 410 × 210 mm gives 6 per layer in a grid on 1,200 × 800 mm, but 12 with 30 mm of overhang all round. The downside: edges get damaged easily, and overhanging walls carry less load.
• Underhang: the load is deliberately kept back from the edge, for example so forks, neighbouring pallets or trailer walls don’t touch the cartons.

JetPallet lets you set either one per pallet side, up to ±500 mm. Every pattern is then calculated on the actual load area.

Which pattern when?

This table is no substitute for checking the individual case. Whether a stack is safe in transit depends on the carton, the contents, the securing and the route.

Layer patterns in JetPallet

JetPallet searches several pattern families automatically – grid, two-block, pinwheel, five-block, recursive rectangle splits and L-shaped arrangements – and checks every result independently for geometry: no overlaps, no carton outside the load area. Layer sequences (repeated, 180°, mirrored) are calculated with a support check, and overhang or underhang is included per side. A layer editor lets you build your own arrangements, which go through the same check.

The quality of the search can be measured. In a test of 1,000 cases, 807 were proven to have no layer with more cartons, and no better solution is known for any case. For the remaining cases, proof is still outstanding. See Limits of the calculation for details and Features for everything else.

Try a pattern quickly in the web calculator. For every pattern family, layer sequence and report, try JetPallet free for 14 days (macOS 15 or later).