32 ECT C flute: box compression and stacking table

32 ECT C flute pairs a 32 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 514 lbf of top-to-bottom compression before any allowance for storage or humidity.

Compression, derated for storage time

BCT after storage losses, lbf, 32 ECT C flute
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	393	248	236	216	196
10 × 8 × 6	446	281	267	245	223
12 × 12 × 12	514	324	309	283	257
14 × 10 × 8	514	324	309	283	257
16 × 12 × 10	556	350	333	306	278
18 × 12 × 12	575	362	345	316	288
18 × 18 × 18	630	397	378	347	315
20 × 16 × 14	630	397	378	347	315
24 × 18 × 18	681	429	408	374	340
24 × 24 × 24	728	458	437	400	364

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 ≈ 493 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	30	15	10	8	5

16 × 12 × 10 in, BCT ≈ 556 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	34	17	12	9	6

20 × 16 × 12 in, BCT ≈ 630 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	38	19	13	10	7

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
29 ECT	-3 lb/in	-9%
40 ECT	+8 lb/in	+25%

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.