48 ECT C flute: box compression and stacking table

48 ECT C flute pairs a 48 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 772 lbf of top-to-bottom compression before any allowance for storage or humidity.

Compression, derated for storage time

BCT after storage losses, lbf, 48 ECT C flute
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	589	371	354	324	295
10 × 8 × 6	668	421	401	368	334
12 × 12 × 12	772	486	463	424	386
14 × 10 × 8	772	486	463	424	386
16 × 12 × 10	833	525	500	458	417
18 × 12 × 12	863	544	518	474	431
18 × 18 × 18	945	595	567	520	473
20 × 16 × 14	945	595	567	520	473
24 × 18 × 18	1,021	643	612	561	510
24 × 24 × 24	1,091	687	655	600	546

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 ≈ 739 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	45	23	15	12	8

16 × 12 × 10 in, BCT ≈ 833 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	51	26	17	13	9

20 × 16 × 12 in, BCT ≈ 945 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	57	29	19	15	10

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
44 ECT	-4 lb/in	-8%
55 ECT	+7 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.