McKee box compression calculator
Estimate the top-to-bottom compression strength of a regular slotted box from its board ECT, caliper and size, or work out the ECT a target strength needs.
Calculator
556 lbf
Estimated BCT, empty box
To reach 600 lbf in C flute at this size, the board needs about 34.6 lb/in ECT.
How it works
- BCT ≈ 5.87 × ECT × √(t × Z), with ECT in lb/in, caliper t in inches and Z = 2(L + W) in inches.
- The inverse gives the ECT needed: ECT = BCT ÷ (5.87 × √(t × Z)).
- McKee, Gander and Wachuta fitted the formula to regular slotted containers; treat other styles and very large boxes with care.
Results are estimates for planning. Confirm critical packs by test. Full method.
Reading the result
Use the result to compare boards and sizes, not to sign off a pack. McKee predicts the strength of a new, dry box loaded evenly on its edges for a short time; storage, humidity and stacking pattern all take strength away.
For a stack, take the required strength from the stacking tool and enter it here as a target to see the lowest ECT that meets it. Taller boxes of the same footprint are not much weaker by this formula, which is one of its known limits.
Sources
- McKee, R.C., Gander, J.W. & Wachuta, J.R. (1963). "Compression strength formula for corrugated boxes." Paperboard Packaging 48(8): 149–159
- Flute calipers: Foster (1997), Wiley Encyclopedia of Packaging Technology
Last reviewed . See all sources and how Packgent computes.