71 ECT EB double wall: box compression and stacking table

71 ECT EB double wall pairs a 71 lb/in edge crush with a nominal 0.188 in caliper. As an empty 12 × 12 × 12 in box, the simplified McKee formula puts it near 1,250 lbf of top-to-bottom compression before any allowance for storage or humidity.

Compression, derated for storage time

BCT after storage losses, lbf, 71 ECT EB double wall
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	955	602	573	525	477
10 × 8 × 6	1,083	682	650	596	541
12 × 12 × 12	1,250	788	750	688	625
14 × 10 × 8	1,250	788	750	688	625
16 × 12 × 10	1,350	851	810	743	675
18 × 12 × 12	1,398	881	839	769	699
18 × 18 × 18	1,531	965	919	842	766
20 × 16 × 14	1,531	965	919	842	766
24 × 18 × 18	1,654	1,042	992	910	827
24 × 24 × 24	1,768	1,114	1,061	973	884

0 days is the McKee estimate itself. Storage losses are Packgent's default assumptions (10 days 37%, 30 days 40%, 90 days 45%, 180 days 50%), not sourced values; edit them in the stacking calculator.

How many high can it stack?

Boxes high, including the bottom one, column stacked for 30 days, before humidity, interlock or overhang losses.

12 × 10 × 8 in, BCT ≈ 1,197 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	72	36	24	18	12

16 × 12 × 10 in, BCT ≈ 1,350 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	82	41	28	21	14

20 × 16 × 12 in, BCT ≈ 1,531 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	92	46	31	23	16

Boxes high = ⌊BCT × (1 − 0.4) ÷ gross weight⌋ + 1. A real stack needs further allowance for humidity, pattern and handling.

Neighbouring grades

Grade	ECT change	BCT change, same flute and size
61 ECT	-10 lb/in	-14%
82 ECT	+11 lb/in	+15%

In McKee, BCT scales directly with ECT, so the percentage change in strength equals the change in ECT.

Freight rule limits

NMFC Item 222 ties each grade to a maximum gross weight and size for LTL shipping. Packgent has not published those limits yet because they could not be checked against the current tariff. See the Item 222 page for status.

Sources

TAPPI T 811: Edgewise compressive strength of corrugated fibreboard (short column test)
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 2026-10-27. See all sources and how Packgent computes.