ECT vs Mullen: two ways to grade board
ECT grades board by how much load a strip carries on its edge; Mullen grades it by how much pressure it takes to burst. ECT predicts stacking, Mullen predicts puncture and rough handling, and neither converts exactly into the other.
What each test measures
The edge crush test (TAPPI T 811 or T 839) stands a short column of board on its edge with the flutes vertical and loads it until it buckles. The result is in pounds per inch of edge.
The burst test (TAPPI T 810) clamps a sheet over a rubber diaphragm and inflates it until the board ruptures. The result is in pounds per square inch, and boxes graded this way are called "200 lb test" and so on.
Why ECT took over for stacking
Boxes in a stack fail by their walls buckling, which is what ECT measures directly. That is why the McKee formula uses ECT, and why a box maker can meet a stacking need with less fibre by grading to ECT.
When burst still matters
Products with sharp corners, rough parcel handling and heavy loose contents test the face of the board more than its edge. For those, burst or puncture resistance is the property to ask about.
Freight classifications list ECT and burst grades side by side. Packgent will publish that table once it is checked against the current edition.
Use it
- Grades
- Ect
- Mullen
- Tappi t 811
- Tappi t 810
- Ect mullen
- Right-sizing boxes to cut dimensional weight
- Reading a box maker's certificate
- Stacking strength and safety factors
Last reviewed 2026-10-27. Formulas and sources: method, sources.