Work out box compression strength instantly with clear inputs, formula shown and shareable results.
The McKee formula predicts box compression strength from board properties and box geometry: BCT = 5.87 x ECT x sqrt(caliper x perimeter). A safety factor of 3-7 is then applied to allow for humidity, storage time, pallet overhang and handling damage, giving the load a box may safely carry in a stack.
McKee formula
BCT (kN) = 5.87 x ECT (kN/m) x sqrt(caliper (m) x perimeter (m))
Safe load
Safe stacking load = BCT / safety factor
Stack heights based on calculated compression strength must be validated by physical testing under the expected humidity, load duration and handling conditions. Collapsing stacks cause serious injuries.
Compression strength falls by around 50% at 90% relative humidity and by a further 30-40% under sustained load over weeks. Pallet overhang, misalignment and vent holes reduce it further.
Yes for stacking performance. ECT measures edgewise compression, which is what actually carries a stacked load; bursting strength relates to puncture and rough handling resistance.