How to palletize boxes: column stack, interlocked or pinwheel and when to use each

1,773 kg against 1,028 kg. That is what the same cardboard box, 49.5 x 33 x 30.5 cm and grade 32 ECT, held in a Rochester Institute of Technology (RIT) test revised in 2021: the first figure with the boxes in column stacks and the second with the boxes interlocked. Before you decide how to palletize boxes from a drawing of the layer, keep that subtraction in mind. The study compares against a single layer of 7 boxes and reports adjusted peak force in pounds: 3,909 and 2,266.

How to palletize boxes: three patterns and what each changes

Column stack. Every layer is the same and each corner lands on another corner. The RIT report explains why it performs: a box carries its load mostly through the corners, which work like posts. If palletizing, stacking and pelletizing get mixed up in your plant, here is the difference.

Interlocked. Each layer is turned or flipped so its joints cross those of the next one, as in a brick wall. The boxes tie into each other, and the corners stop lining up.

Pinwheel. Four blocks turn around the center, often with a gap. On a 1.00 x 1.00 m pallet, a 40 x 30 cm box gives 8 per layer in pinwheel and leaves a 20 x 20 cm gap; with all boxes the same way it gives 6 (Target Robotics calculation, zero overhang).

The drawing of the layer and the rule between layers are two separate decisions. A 6+4 mixed layer repeated identically on every level leaves corner on corner and behaves like a column stack. That same layer mirrored on every other level comes out interlocked. Before you argue about patterns, ask which of the two things is being proposed.

How much compression does each pattern lose?

RIT tested single wall C-flute corrugated boxes in 32 and 44 ECT, with five replications per pattern, and compared each stack against a single layer of 7 boxes. The last column is the reference value from the Fibre Box Handbook, according to the Fibre Box Association (2021) and the report itself.

We owe you a note on pinwheel. RIT did not test it. A Michigan State University thesis (Kim, 1993) includes it, and we could not consult its results. By geometry we expect that, flipped between layers, it behaves closer to interlocked than to column stack, because the corners stop lining up. That is our own reasoning, with no figure behind it.

On stability, the sources agree on the direction and none gives a number. RIT notes that interlocked is more stable than column stack with the same boxes, and the World Food Programme guide (2022) warns that a stack with no interlocking is more likely to fall over.

When should you use column, interlocked or pinwheel?

The boxes per pallet table answers how many boxes each option gives, and you can see the alternate layer drawn out in the calculator.

What if you interlock only the top layers?

That is the idea behind the hybrid: strength below and tie-in above. The RIT data does not favor it, with 45 to 49% loss in a pattern that hoped to resemble a column stack. Its authors note that a small offset, about 0.6 cm, would keep far more strength than the hybrid. If the box has little strength to begin with, interlocking the top hardly gives back what was lost.

How to build the pallet, step by step

1. Gather the data that drives the decision. Box weight, BCT, pallet size and the maximum height of whoever receives it.
2. Measure the filled box and choose the layer. Use the outside dimension, with bulge.
3. Decide the rule between layers. Repeating the layer gives you a column stack; flipping it gives you interlocked.
4. Start flush with the edge. With zero overhang and no gaps between boxes, because the first layer sets the position of all the others.
5. Check the alignment on each layer. In a column stack, corner on corner: a 1.3 cm offset has already been measured at 28% loss (Singh, cited by RIT).
6. Put the heaviest on the bottom. If the pallet carries different products, NOM-006-STPS-2023, the standard from Mexico’s labor ministry (STPS) on storing and handling materials, requires it in section 9.4(g).
7. Tie in and mark. Choose the tie-in according to the pattern; how to stretch wrap a pallet covers the film. The same standard requires marking the maximum stack height in the storage area (section 9.3(h)).

Mistakes that cost more than the pattern

Offset from careless stacking. A Singh study cited by RIT reports 28% loss with a 1.3 cm offset and 43% with 2.5 cm. RIT measured 44 to 45% with 1.9 cm, and calls it an extreme case. A poorly aligned column stack can cost almost as much as interlocking, with none of the tie-in in return.

Overhang. Virginia Tech measured 0 to 40% loss on boxes that stick out past the pallet, against the 20 to 40% the Handbook estimates (Molina and Horvath, 2024). Its report ties the loss to how far the box sticks out, on which side, and to the box perimeter.

Humidity and time. IPS Packaging publishes as generally accepted multipliers 20% loss at 70% relative humidity, 52% at 90%, and 40% after 30 days under load (checked November 3, 2026). It is a secondary source and does not cite its origin; use it as an order of magnitude and test with your own board.

Half-filled boxes on the bottom. The World Food Programme guide (2022) asks to keep them out of the lower layers, because a collapse starts there.

A quick calculation to see if your box holds up

Target Robotics calculation with assumptions: a 12 kg box and 6 layers, which puts 5 x 12 = 60 kg on each box at the bottom. RIT multipliers for the pattern, and IPS Packaging multipliers for 70% humidity (0.80) and 30 days under load (0.60). No additional safety factor.

The ratio between the two columns is 0.84 / 0.49 = 1.71. Interlocking the same load calls for a box with about 71% more strength. Multiplying factors is a simplification, and it helps you decide what to test. Your corrugated supplier sets the number with a test of your box.

What changes when a robot does the stacking?

Repeatability. A robot takes the same compression losses for each pattern. Since offset weighs so heavily in the table, programmed placement can hold the position of every box shift after shift, and changing patterns becomes a matter of programming and, sometimes, of tooling. Target Robotics has palletized up to 60 boxes per minute (company presentation, May 2026) and boxes of 3 to 50 kg (MMS México, 2017); the case palletizer robot page says what data is needed, and manual vs robotic palletizing compares cost and injuries.

Ask your corrugated supplier for the BCT of your box at the humidity of your warehouse, and test a full pallet with the chosen pattern: RIT tested two board grades and a single box size.