ECT-32 vs ECT-44 — what the corrugated rating actually tells you about your box.

What ECT is, in one sentence

Edge Crush Test (ECT) measures the force, in pounds per linear inch, that a corrugated board can withstand on its edge before crushing. ECT-32 means 32 lb/in. ECT-44 means 44 lb/in. Higher = stronger when boxes are stacked on top of each other.

ECT replaced the older "Mullen burst test" as the standard rating for stacking strength. Mullen measures resistance to puncture; ECT measures resistance to compression. For palletized shipping, ECT is what matters.

When ECT-32 is enough

ECT-32 single-wall corrugated is the workhorse of e-commerce and light-industrial shipping. It handles:

• Boxes up to roughly 35 lb of contents.
• Stacked pallets up to 4 high in dry, climate-controlled warehouses.
• Standard parcel and LTL shipping with normal handling.

When you need ECT-44 (or higher)

• Box contents exceed 35 lb.
• Pallets stack 5+ boxes high in storage.
• Humidity is a factor. Corrugated loses ~50% strength at high humidity.
• Long freight times, especially cross-country LTL with multiple cross-docks.
• High-value contents where damage cost outweighs the ~15–20% packaging cost premium.

Double-wall: BC, EB, AB

Double-wall corrugated uses two fluted layers laminated between three liners.

• BC double-wall (B-flute + C-flute) — ECT-44 to 48 — heavy goods, stacked loads.
• EB double-wall (E-flute + B-flute) — premium retail with strength.
• AB double-wall — used for very heavy industrial / agricultural product.

Practical decision rules

Scenario	Recommended grade
E-commerce mailer, < 5 lb	ECT-32 single-wall E or B-flute
Standard parcel, 5–25 lb	ECT-32 C-flute
Heavy retail, 25–50 lb	ECT-44 C-flute
Industrial parts, > 50 lb	BC double-wall ECT-48
Cold chain / outdoor storage	Always one grade up from dry equivalent

A note on weight vs strength

ECT measures stacking strength, not puncture resistance. For sharp-edged or pointed contents, specify higher liner weight in addition to a higher ECT. For drop-test concerns, the right answer is usually internal protection (foam inserts, void fill) plus appropriate corrugated, not ECT alone.