Package Structural Design Calculator

This calculator applies the McKee formula — the industry-standard equation for estimating a corrugated box's top-to-bottom compression strength — directly: BCT = 5.87 × ECT × √(caliper × perimeter), where ECT is the board's Edge Crush Test rating (its resistance to crushing along the flute direction), caliper is the board's thickness, and perimeter is twice the sum of the box's length and width. That BCT figure represents the load at which the box would fail, so the calculator divides it by a 3x safety factor (a common warehouse-stacking standard) to get a safe stacking weight, then divides that by your product weight to find how many boxes high you can safely stack a single column. It separately works out how many boxes fit on one layer of a standard 48×40-inch pallet and uses that, together with the safe stack weight, to estimate the maximum number of full pallet layers.

Because BCT scales with the square root of both caliper and perimeter but linearly with ECT, doubling a board's ECT rating roughly doubles its strength, while doubling the box's footprint only increases strength by about 41% — a detail worth knowing if you're deciding whether to upgrade board grade or shrink the box to hit a stacking target. The board-grade output (1-3, roughly 200#/275#/350# test equivalents) and the burst-strength estimate are rough correlations to ECT, not independently measured values, and the McKee formula itself is an empirical approximation validated for typical corrugated constructions — it can diverge from real-world performance for unusual flute combinations or extreme humidity, so treat this as a design-stage estimate to be confirmed with an actual BCT lab test before finalizing packaging for heavy or high pallet-stack applications. Box height is collected for reference but doesn't currently factor into the McKee formula or any other calculated result here — compression strength depends on the box's footprint (length and width), not its height.