44 ECT B flute: box compression and stacking table

44 ECT B flute pairs a 44 lb/in edge crush with a nominal 0.125 in caliper. As an empty 12 × 12 × 12 in box, the simplified McKee formula puts it near 633 lbf of top-to-bottom compression before any allowance for storage or humidity.

Compression, derated for storage time

BCT after storage losses, lbf, 44 ECT B flute
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	483	304	290	266	242
10 × 8 × 6	548	345	329	301	274
12 × 12 × 12	633	399	380	348	316
14 × 10 × 8	633	399	380	348	316
16 × 12 × 10	683	431	410	376	342
18 × 12 × 12	707	446	424	389	354
18 × 18 × 18	775	488	465	426	387
20 × 16 × 14	775	488	465	426	387
24 × 18 × 18	837	527	502	460	418
24 × 24 × 24	895	564	537	492	447

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 ≈ 606 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	37	19	13	10	7

16 × 12 × 10 in, BCT ≈ 683 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	42	21	14	11	7

20 × 16 × 12 in, BCT ≈ 775 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	47	24	16	12	8

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
40 ECT	-4 lb/in	-9%
48 ECT	+4 lb/in	+9%

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.