44 ECT C flute: box compression and stacking table

44 ECT C flute pairs a 44 lb/in edge crush with a nominal 0.156 in caliper. As an empty 12 × 12 × 12 in box, the simplified McKee formula puts it near 707 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 C flute
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	540	340	324	297	270
10 × 8 × 6	613	386	368	337	306
12 × 12 × 12	707	446	424	389	354
14 × 10 × 8	707	446	424	389	354
16 × 12 × 10	764	481	458	420	382
18 × 12 × 12	791	498	474	435	395
18 × 18 × 18	866	546	520	476	433
20 × 16 × 14	866	546	520	476	433
24 × 18 × 18	936	589	561	515	468
24 × 24 × 24	1,000	630	600	550	500

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 ≈ 677 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	41	21	14	11	7

16 × 12 × 10 in, BCT ≈ 764 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	46	23	16	12	8

20 × 16 × 12 in, BCT ≈ 866 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	52	26	18	13	9

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.