51 ECT BC double wall: box compression and stacking table

51 ECT BC double wall pairs a 51 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 1,100 lbf of top-to-bottom compression before any allowance for storage or humidity.

Compression, derated for storage time

BCT after storage losses, lbf, 51 ECT BC double wall
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	840	529	504	462	420
10 × 8 × 6	953	600	572	524	476
12 × 12 × 12	1,100	693	660	605	550
14 × 10 × 8	1,100	693	660	605	550
16 × 12 × 10	1,188	749	713	654	594
18 × 12 × 12	1,230	775	738	676	615
18 × 18 × 18	1,347	849	808	741	674
20 × 16 × 14	1,347	849	808	741	674
24 × 18 × 18	1,455	917	873	800	728
24 × 24 × 24	1,556	980	933	856	778

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 ≈ 1,053 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	64	32	22	16	11

16 × 12 × 10 in, BCT ≈ 1,188 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	72	36	24	18	12

20 × 16 × 12 in, BCT ≈ 1,347 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	81	41	27	21	14

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
48 ECT	-3 lb/in	-6%
61 ECT	+10 lb/in	+20%

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.