Palletization Explained: Meaning, Stacking Patterns and Standard Pallet Sizes in India

Palletization is the practice of stacking cartons, sacks, drums or components on a pallet in a defined pattern and then securing them, usually with stretch film and strapping, so that the whole stack is handled as one unit load. The word is spelt palletisation in Indian and British usage and palletizing in most machinery catalogues; they mean the same thing. The point of the exercise is that a forklift moves 1,000 kg in one lift and drops nothing, while a loader moving the same 40 cartons by hand drops, drags and mis-stacks several of them on every truck.

Getting it right involves four decisions: the pallet footprint, the stacking pattern, the load height, and the securing method. Each one has a number attached to it, and each one is a place where Indian consignments routinely go wrong.

Standard pallet sizes: the six ISO footprints and what India actually uses

ISO 6780 recognises six pallet footprints. The table shows them alongside the region that uses each and how many fit on the floor of a standard container. Internal container floor is roughly 5.9 × 2.35 m for a 20 ft and 12.03 × 2.35 m for a 40 ft.

In India the 1200 × 1000 mm four-way pallet is the default for warehouses, 3PL operations and general export. Exporters to Europe often shift to 1200 × 800 mm because the customer's racking and lorries are dimensioned for it, and a 1200 × 1000 mm load can be refused or re-palletised at the buyer's cost. Automotive Tier-1 suppliers and FMCG plants increasingly run 1200 × 1000 mm plastic pallets in closed loops because they are washable, consistent in dimension and free of the ISPM-15 heat-treatment requirement that applies to solid wood in export consignments.

Whatever the footprint, check the pallet's rating. Typical four-way wooden pallets are rated for 1,000–1,500 kg dynamic load (moving on a forklift) and considerably more static; injection-moulded plastic pallets are commonly rated 1,000 kg dynamic. Overloading a pallet does not usually break it; it bends the deck boards, which tilts the bottom cartons and starts the collapse.

Stacking patterns: column versus interlock, and what each costs you

A corrugated carton carries nearly all its vertical load at its four corners. That single fact decides the stacking question.

• Column stacking places every carton directly above the one below, corner over corner. Load passes straight down the vertical edges, so the stack retains the full box compression strength (BCT) of the carton. The weakness is lateral: a column stack has no interlocking, so it relies entirely on film, strapping or corner boards to stay upright.
• Interlocked (brick) stacking rotates alternate layers by 90° so cartons bridge the joints below. The block is far more resistant to toppling, but corners no longer align, so part of each carton's load lands mid-panel where the board is weakest. Published figures for the loss range from about 20% to 45% of stacking strength depending on carton proportions and the number of interlocked layers.
• Pinwheel is an interlock variant that leaves a central void; it stabilises square-ish cartons but wastes 5–10% of the footprint and should be avoided for heavy loads.

The practical rule we give customers: column stack, and buy stability from corner boards and stretch film rather than from the pattern. Interlock only the top layer if the load is tall and the truck route is rough. If you must interlock throughout, specify the carton for the extra load. The edge crush test value is the number that drives box compression strength, and a 5-ply carton will usually cover a 20–45% loss where a 3-ply will not.

The overhang rule and the underhang trap

Cartons must sit inside the pallet edge. A carton that overhangs loses the deck support under its outer edge, so the corner that should be carrying the load is hanging in air and the panel next to it takes the load instead. Testing published in the corrugated industry's reference handbooks puts the loss at roughly a third of compression strength for a 25 mm overhang, and it gets worse quickly beyond that. Overhung cartons are also the ones a forklift tine catches, the ones that rub against the container wall, and the ones a stretch film cannot pull inward.

The opposite mistake, underhang, is subtler. A load that stops 100 mm short of the pallet edge on each side is fine structurally, but it wastes 15–20% of the container footprint and lets the load shift on the deck under braking unless it is strapped down. The usual answer is to size the carton so that the pallet pattern fills the deck to within about 25 mm. A carton footprint of 400 × 300 mm gives a clean 10-per-layer pattern on 1200 × 1000 mm; 600 × 400 mm gives 5 per layer; 300 × 200 mm gives 20. If you are still designing the carton, start from the pallet and work back.

Load height, stability and the stacking calculation

Three limits govern how high you can go. The first is the vehicle: a 20 ft or 40 ft container door is 2.28 m high, so with a 150 mm pallet the practical ceiling is about 2.0 m of load. Standard 32 ft Indian container trucks run similar internal heights; open-body trucks are limited by tarpaulin and the loader's reach rather than by any standard. The second is stability: once a load is taller than about 1.5 times the pallet's shorter side it becomes top-heavy and needs strapping through the pallet, not only stretch film. Most warehouses settle on 1.2–1.8 m all-in. The third is compression, which is a calculation rather than a rule of thumb.

Worked example: cartons weigh 20 kg each, stacked 6 high in a column pattern, and the pallets will be double-stacked in the warehouse for 30 days in monsoon humidity. The bottom carton on the lower pallet carries the 5 cartons above it (100 kg) plus the whole upper unit load divided across the 10 columns (another 120 kg plus the pallet's share), call it 230 kg. Apply a safety factor for duration and humidity, commonly 3 to 5 for long storage in humid conditions, and the carton needs a BCT of roughly 700–1,150 kgf. That is a 5-ply board at a good ECT, or a 7-ply if the stack is any taller. Check the number against the McKee formula or with a compression test to IS 2771 rather than by trusting the ply count alone.

Moisture deserves its own line. Corrugated board loses a large share of its compression strength as it takes up moisture; a carton stored at 85–90% relative humidity through a Gujarat or Mumbai monsoon can lose half its dry-condition BCT. If loads sit in an unconditioned godown from July to September, size for it.

Securing the unit load: corner boards, strapping and stretch film

A unit load is only a unit load if it arrives as one. Three components do the securing, and they do different jobs.

The stretch film step is where most loads fail and where the fix costs least. Film must be anchored to the pallet itself, with the first turns wrapping over the deck edge, or the cartons are a block that slides off a deck it was never attached to. Film must reach the top corners with full tension, not taper off. And a machine applying 200–250% pre-stretch holds the load better than a hand wrap with more film on it because pre-oriented film resists creep. We cover the application detail in pallet wrapping best practices to prevent load collapse; the material itself is described under stretch film, and for container consignments we normally supply 23 micron stretch film because carton corners and crate edges puncture anything thinner over a 15-day sea journey.

Corner boards are the component Indian shippers most often leave out and most often regret. A corner protector along each vertical edge does three things at once: it stops strapping and film from crushing the carton corners, it adds measurable vertical strength to the stack, and it gives the film a firm edge to tension against so the load is pulled square instead of pulled round.

How to write a palletization specification: checklist

A pallet spec on the packing instruction sheet removes most of the variation between shifts and between packers. Cover these twelve points.

1. Pallet footprint and type (1200 × 1000 mm four-way wooden, heat-treated and ISPM-15 stamped for export; or plastic).
2. Pallet rating (dynamic load) and whether pallets may be double-stacked in storage.
3. Carton external dimensions and the pattern per layer, drawn, with cartons per layer.
4. Layers per pallet and total cartons per pallet.
5. Stacking method: column; interlocked; or column with interlocked top layer.
6. Maximum overhang: nil, or not more than 10 mm any side.
7. Maximum load height including pallet, and gross weight per pallet.
8. Slip sheet between pallet and first layer where the deck boards could mark or puncture the cartons.
9. Corner boards: size, thickness and number (usually 4, full height).
10. Strapping: material, width, number and direction of straps, tension method.
11. Stretch film: gauge, width, pre-stretch if machine applied, overlap, turns top and bottom, and that the film is anchored to the pallet.
12. Labelling: pallet label position, arrows, "do not double stack" or "max 2 high" mark, and the ISPM-15 mark visible on two sides for export.

Then test it once. A pallet loaded to specification and driven 50 km on a local road, or put through a vibration and incline-impact test at a lab, tells you more than any amount of desk calculation.

Where the cartons and film come from

Palletization works when the carton, the cushioning inside it and the securing materials were specified together, because a carton that is 30 mm too wide for the pallet pattern or 20% short on ECT undoes everything above. If you send us the product weight, the pallet footprint you ship on and the stack height, we will size the carton to the pallet pattern, specify ply and ECT for the stacking load, and supply the corner boards, strapping and stretch film to match. For export loads, the export packaging page covers container stuffing, ISPM-15 and the corrugated-plus-foam constructions that replace timber crates; the palletizing glossary entry is the short version of this article.