71 ECT BC double wall: box compression and stacking table

71 ECT BC double wall pairs a 71 lb/in edge crush with a nominal 0.281 in caliper. As an empty 12 × 12 × 12 in box, the simplified McKee formula puts it near 1,531 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 BC double wall
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	1,170	737	702	643	585
10 × 8 × 6	1,326	836	796	729	663
12 × 12 × 12	1,531	965	919	842	766
14 × 10 × 8	1,531	965	919	842	766
16 × 12 × 10	1,654	1,042	992	910	827
18 × 12 × 12	1,712	1,079	1,027	942	856
18 × 18 × 18	1,876	1,182	1,125	1,032	938
20 × 16 × 14	1,876	1,182	1,125	1,032	938
24 × 18 × 18	2,026	1,276	1,216	1,114	1,013
24 × 24 × 24	2,166	1,364	1,299	1,191	1,083

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 ≈ 1,466 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	88	44	30	22	15

16 × 12 × 10 in, BCT ≈ 1,654 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	100	50	34	25	17

20 × 16 × 12 in, BCT ≈ 1,876 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	113	57	38	29	19

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.