26 ECT E flute: box compression and stacking table

26 ECT E flute pairs a 26 lb/in edge crush with a nominal 0.063 in caliper. As an empty 12 × 12 × 12 in box, the simplified McKee formula puts it near 264 lbf of top-to-bottom compression before any allowance for storage or humidity.

Compression, derated for storage time

BCT after storage losses, lbf, 26 ECT E flute
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	202	127	121	111	101
10 × 8 × 6	229	144	137	126	114
12 × 12 × 12	264	167	159	145	132
14 × 10 × 8	264	167	159	145	132
16 × 12 × 10	286	180	171	157	143
18 × 12 × 12	296	186	177	163	148
18 × 18 × 18	324	204	194	178	162
20 × 16 × 14	324	204	194	178	162
24 × 18 × 18	350	220	210	192	175
24 × 24 × 24	374	236	224	206	187

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 ≈ 253 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	16	8	6	4	3

16 × 12 × 10 in, BCT ≈ 286 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	18	9	6	5	3

20 × 16 × 12 in, BCT ≈ 324 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	20	10	7	5	4

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
23 ECT	-3 lb/in	-12%
29 ECT	+3 lb/in	+12%

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.