Packaging logistics: packout, pallets & freight

Logistics is a design decision, not a shipping-dock problem

Ask a packaging engineer where shipping cost comes from and they'll point upstream — to a whiteboard, weeks before the first truck is booked. The dimensions of the primary package, the number of units in a case, the height of that case, the grade of corrugated in the shipper: those choices decide how efficiently the product fills a pallet, how high it can stack without crushing, and how it rates for freight. By the time a load reaches the dock, the cost is mostly already spent.

That's the core idea of packaging logistics. The journey of a product — unit into case, case onto pallet, pallet into truck — is a chain, and small inefficiencies at one link multiply down the whole thing. A case a half-inch too tall to fit one more layer under the trailer ceiling; a footprint that leaves the pallet deck a tenth uncovered; a box one grade too light, so it stacks two high instead of three. None of these show up in a design review that only looks at the shelf; all of them show up on every freight invoice for the life of the SKU.

This guide walks the chain from the inside out: the case pack, the pallet, box strength, how a truck actually fills, how freight is classed and priced, dimensional weight, and protecting the load. It's the pillar for our logistics cluster — each section links to a deeper dive.

The shipping unit: the case pack

Everything in distribution is counted in cases. The case pack — also called the master carton or shipper — is the corrugated box that holds a fixed number of selling units, and it's the atomic unit of the supply chain: warehouses receive cases, pick cases, and palletize cases. Get the case pack right and the pallet, the truck, and the freight bill tend to fall into place.

Three things drive a good case pack:

• Count and layer math. Retailers and distribution centers often specify units per case, and sometimes cases per layer and per pallet. Counts that divide cleanly into pallet layers waste less space than awkward ones.
• Handling weight. A case a person lifts by hand is usually kept to a manageable weight — general ergonomic guidance, such as the NIOSH lifting equation, points toward lighter, more frequent lifts to reduce injury risk. Heavier cases may need two-person handling or mechanical aids.
• Outer dimensions. For logistics, the case's outside dimensions matter more than the count inside. Those dimensions decide how the case tiles onto a pallet. A case sized to a clean fraction of the pallet footprint palletizes tightly; an odd size leaves gaps you then pay to ship as air.

The lesson: design the case to the pallet, not just to the product. A few millimeters off the case footprint can be the difference between a full pallet layer and a wasteful one — which is exactly the tiling problem we work through in how many boxes fit on a pallet.

Pallet math: Ti-Hi and the 48 × 40 standard

Once the case is set, the question becomes how many fit on a pallet. The answer has a name: Ti-Hi.

In North America the default pallet is the GMA pallet, a 48 × 40-inch hardwood platform (named for the former Grocery Manufacturers Association), whose deck gives roughly 1,920 square inches of usable footprint per layer. Ti — cases per layer — is a tiling problem: it depends on the case's outer length and width and how you rotate them to cover the deck without overhanging the edges. Hi — layers high — depends on the height you can build to and whether the bottom cases can carry the weight above them.

Cases should cover the deck without overhang (cases hanging past the pallet edge, which strips a large share of a box's compression strength and invites damage) and without severe underhang (a footprint smaller than the deck, which wastes cube). The goal is a stable, fully covered layer.

How you arrange cases within each layer is the stacking pattern, and it's a genuine trade-off:

Pattern	How cases sit	Stacking strength	Stability
Column stack	Directly on top of each other, corner over corner	Highest — corners carry the load	Lower — the stack can shear or lean
Interlocked / brick	Rotated layer to layer so cases bridge the seams below	Reduced — corners no longer align	Higher — the layers tie together
Pinwheel	Cases arranged around a center, alternating each layer	Between the two	Good fit for certain case footprints

A column stack is strongest because every case sits corner-over-corner on the one below, and the corners of a box carry most of its load. An interlocked (brick) pattern rotates alternating layers so cases bridge the seams beneath them; that ties the load together and resists leaning, but it sacrifices stacking strength because the corners no longer line up. A common rule of thumb is that interlocking can give up a large share — often cited as up to about half — of a column's compression strength. Which pattern wins depends on the box, the product, and how the load is handled; the full trade-off, with the pallet math worked through, is in our deep dive on Ti-Hi, BCT and freight class.

Box strength: ECT, BCT, and the McKee estimate

Whether you can stack cases six layers high — or stack finished pallets three high in a warehouse — comes down to box strength, and two numbers matter most:

• ECT (Edge Crush Test) measures the stiffness of the corrugated board itself, in pounds per inch of edge. It's a property of the board, before it becomes a box. (The older Mullen / burst test measures puncture resistance instead, and is a different way to spec board.)
• BCT (Box Compression Test) measures the whole finished box's top-to-bottom compression strength, in pounds — how much load it can bear before it crushes. This is the number that governs stacking.

You can estimate BCT from ECT without building and crushing a box, using the McKee formula. In its common simplified form, box compression is roughly proportional to the board's ECT, the square root of the board caliper (thickness), and the square root of the box perimeter:

BCT ≈ 5.87 × ECT × √(caliper × perimeter)

Treat this as an estimate, not a guarantee. McKee assumes a regular slotted container in good condition under ideal, short-term lab loading. Real warehouses are not ideal, so engineers apply a safety factor — often somewhere in the range of 3× to 7× the actual static load, depending on how the factors below stack up:

Factor	Effect on real-world stacking strength
Storage time	The longer a box sits under load, the more it creeps and weakens; strength is far lower after weeks than after minutes
Humidity	Corrugated absorbs moisture; sustained high humidity can cut strength dramatically — roughly halving it at very high relative humidity is a common rule of thumb
Pallet overhang	Cases hanging past the pallet edge lose a large share of their compression strength
Misalignment / interlocking	Corners not stacked corner-over-corner carry far less load
Box condition	Ventilation holes, hand slots, prior handling, and reused board all reduce strength

In short, the BCT you measure in a lab is the ceiling; the load you should plan for is a fraction of it — which is why two boxes with the same ECT can perform very differently in a humid warehouse than a climate-controlled one. Corrugated deserves its own treatment, which we give it in our guide to corrugated box strength.

Cube vs weight: what fills the truck first

A trailer has two ceilings: a volume ceiling (how much space is inside) and a weight ceiling (how much payload it can legally carry). On US Interstates the federal gross-vehicle-weight limit is generally 80,000 pounds, and after the tractor and trailer's own weight, the usable payload is a good deal less. Every full load runs into one ceiling before the other:

• Cube out — you run out of space before you reach the weight limit. This is the world of light, bulky product: pillows, empty bottles, foam, most e-commerce. The trailer is full but well under its weight limit.
• Weigh out — you hit the weight limit before the space is full. This is dense product: liquids, hardware, printed materials. The floor is loaded to the axle limit with room to spare above.

Knowing which one your product hits changes what you optimize. If you cube out, every cubic inch of wasted package — void space, oversized boxes, air — is money, so right-sizing pays directly. If you weigh out, shaving package weight (without giving up protection) buys you more product per truck, while a slightly larger box may cost nothing. The same design change can be a win or a waste depending on which ceiling you're against.

Freight class and density

Full truckloads (FTL) are priced by the truck. But a lot of packaging moves as less-than-truckload (LTL) — a few pallets sharing a trailer with other shippers' freight — and LTL is priced using freight class.

Freight class comes from the National Motor Freight Classification (NMFC), maintained by the NMFTA, which sorts commodities into 18 classes from 50 to 500. A lower class is cheaper to ship; a higher class costs more. The single biggest driver of class is density — pounds per cubic foot — calculated from the total weight and total cube of the shipment, pallet included. Denser freight generally lands in a lower class. A rough, representative version of the density guideline looks like this:

Density (lb / ft³)	Typical class
50 and up	50
30 – 35	60
15 – 22.5	70
10.5 – 12	92.5
9 – 10.5	100
6 – 7	150
4 – 5	200
2 – 3	300
1 – 2	400
under 1	500

Read this as guidance, not gospel. The real classification depends on the item's specific NMFC code, and it weighs more than density: stowability, handling, and liability all factor in, and some commodities carry a fixed class regardless of density. Always confirm the class for your product with your carrier or the NMFTA rather than reading it off a chart. The density-to-class interaction, and the pallet math behind it, is covered alongside Ti-Hi, BCT and freight class.

Dimensional weight

Parcel carriers — the ones that move individual boxes rather than pallets — solved the cube-versus-weight problem with dimensional weight (DIM weight). Instead of billing purely by scale weight, they bill the greater of the actual weight and a volumetric weight derived from the package's size.

The math is simple. Multiply length by width by height to get cubic size, then divide by a DIM divisor the carrier publishes:

DIM weight = (L × W × H) ÷ divisor

For many domestic US services the divisor has commonly been around 139 (cubic inches per pound), but this is exactly the kind of number that varies by carrier and changes over time — treat it as illustrative and verify the current divisor for your service. Because carriers bill the greater of the two weights, an oversized box full of air can be charged as if it were heavy. The fix is the same one that helps you cube out less on a pallet: right-size the box. A package cut down to its contents lowers both its DIM weight and its damage risk. We break it down further in dimensional weight, explained.

Damage and protection

Cheaper freight is a false economy if the product arrives broken. Protecting the load is the last link, and it's mostly about controlling movement and carrying the stack:

• Fill the void. Empty space lets product shift and lets boxes collapse inward. Void fill, molded pulp, foam-in-place, and inner cartons keep contents from moving — and right-sizing the box reduces void in the first place.
• Protect the edges and corners. Because a box carries load through its corners and edges, edge boards and corner protectors reinforce exactly where the compression goes, and let a load stack higher.
• Unitize the pallet. Stretch wrap, banding, and top caps turn a pile of loose cases into a single unit that resists shifting in transit. A well-unitized pallet holds its pattern — and therefore its strength.
• Test to a standard. Rather than guessing, packaging is validated against distribution-testing standards such as the ISTA series and ASTM D4169, which simulate the drops, vibration, and compression of real shipping lanes. Test to the profile that matches how your product actually ships; the standards themselves are the authority on method and acceptance.

The full Logistics library

This guide is the overview. Each link below is a focused deep-dive into one part of the chain:

• Ti-Hi, BCT & freight class — the pallet math buyers actually run: cases per pallet, how box compression limits your stack, and how the load rates for freight.
• How many boxes fit on a pallet? — working the tiling problem on a 48 × 40 deck, from case footprint to Ti to a full pallet count.
• Corrugated box strength — ECT versus BCT, the McKee estimate, flutes and board grades, and what really derates strength in a warehouse.
• Dimensional weight, explained — how parcel carriers charge for size, how to calculate DIM weight, and how right-sizing lowers the bill.

How PackOS handles the logistics layer

Because PackOS starts from the actual dieline and dimensions of a package, it already knows the geometry that drives all of this — so it can carry the math forward. From the case and product dimensions it can work out how cases tile onto a standard pallet, estimate cube and density, and surface the logistics implications of a spec while the package is still being quoted, not after the first shipment. You can see where this fits on the technology page, or run a real file through Quick Quote and get the packaging priced in about a minute.