Box Compression Strength Calculator

Work out box compression strength instantly with clear inputs, formula shown and shareable results.

About Box Compression Strength Calculator

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.

Formulas

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

Worked example

With the default values below, Box Compression Strength Calculator returns Box Compression Strength of 118.80. Change any input above and every figure here is recalculated in your browser.

Inputs used

Edge Crush Test (ECT)minimum 0.01 kN/m: 8 kN/m
Board Caliperminimum 0.01 mm: 4 mm
Box Perimeterminimum 1 mm: 1,600 mm
Design Safety Factorminimum 1: 5

Results

Box Compression Strength: 118.80
Safe Stacking Load: 23.76
Safe Load In Kilograms: 2,422.03
Box Perimeter: 1.600

Step by step

1Values used
2McKee formula
3Safe load
4Box Compression Strength= 118.80
5Safe Stacking Load= 23.76
6Safe Load In Kilograms= 2,422.03
7Box Perimeter= 1.600

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
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.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

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.

Frequently Asked Questions

Why such a large safety factor?

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.

Is ECT better than bursting strength for specifying board?

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.