If you are new to buying boxes it is important to know a few things.
Measure Boxes the Right Way!

Length  x  Width  x  Height

The longer side of a box is the length.  The shorter is the Width.  The spine of the box is the height or depth.

"L" Always measure a box by the length first.  This is always the horizontal measurement of the assembled box front.

"W" The width is the measurement of the box from front to back.  This is always the sides of the assembled box.

"H" The height or depth is the last measurement.  It is the vertical measurement of the assembled box.  Also, top to bottom as it sits. 

The strength of a box is commonly measured in Edge Crush (ECT), Gross Weight Limit (lbs), and Bursting Strength (Test). This information lets you know how much weight can be put into each box and how much weight can be stacked on the boxes. Every box made in North America has a stamp on it that states the pertinent information for each carton. Test is an industry term for the bursting strength of the box, as measured in how much weight it can hold. Weight is the actual pounds a box can safely contain without damage. Edge Crush Test (ECT) is the pounds per square inch strength. Here is a conversion chart so you can compare the scale for each measurement:

1. Bursting Strength (MULLEN)	2.  Maximum Weight Limit	3. Edge Crush Test (ECT)
125 Test	20 Lbs	23 ECT
150 Test	35 lbs	26 ECT
175 Test	50 lbs	29 ECT
200 Test	65 lbs	32 ECT
275 Test	95 lbs	44 ECT
350 Test	120 Lbs	55 ECT

1. Bursting Strength (MULLEN)	2. Maximum Weight Limit	3. Edge Crush Test (ECT)
200Test	80 Lbs	42 ECT
275 Test	100 lbs	48 ECT
350 Test	120 lbs	51 ECT
400 Test	140 lbs	61 ECT
500 Test	160 lbs	71 ECT
600 Test	180 Lbs	82 ECT