32 ECT B flute: box compression and stacking table

32 ECT B flute pairs a 32 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 460 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 B flute
Inside size, in	0 days	10 days	30 days	90 days	180 days
8 × 6 × 4	351	221	211	193	176
10 × 8 × 6	398	251	239	219	199
12 × 12 × 12	460	290	276	253	230
14 × 10 × 8	460	290	276	253	230
16 × 12 × 10	497	313	298	273	248
18 × 12 × 12	514	324	309	283	257
18 × 18 × 18	564	355	338	310	282
20 × 16 × 14	564	355	338	310	282
24 × 18 × 18	609	383	365	335	304
24 × 24 × 24	651	410	390	358	325

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 ≈ 441 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	27	14	9	7	5

16 × 12 × 10 in, BCT ≈ 497 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	30	15	10	8	5

20 × 16 × 12 in, BCT ≈ 564 lbf
Gross weight per box	10 lb	20 lb	30 lb	40 lb	60 lb
Boxes high	34	17	12	9	6

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.