The corrugated industry determines strength with two tests. The long time standard has been the Bursting (Mullen) Test which is a measure of the force needed to rupture or puncture the face of a corrugated board. This is measured by the Mullen Tester. The Bursting strength is reported in pounds (for example, 275#). A newer standard is the Edge Crush Test (ECT). This is directly related to the stacking strength of a carton and boxes. The ECT is a measure of the edgewise compressive strength. To use this measurement, it is measured in pounds per lineal inch of load bearing edge (lb/in). However, you will usually see this value reported as an ECT.