Dimensions are given in the sequence of length, width and depth. Internationally, the words length, breadth and height may be used to express these dimensions. The dimensions of a box are described based on the opening of an assembled box, which can be located on the top or the side, depending on how it is to be filled. The opening of a box is a rectangle; that is, it has two sets of parallel sides. The longer of the two sides is considered its length, the shorter of the two sides is considered its width. The side perpendicular to length and width is considered the depth of the box.

Dimensions can be specified for either the inside or the outside ofthe box. Accurate inside dimensions must be determined to ensure the proper fit for the product being shipped or stored. At the same time, palletizing and distributing the boxes depends on the outside dimensions. The box manufacturer should be informed as to which dimension is most important to the customer.

McKee also created a simpler formula based on caliper of the combined board instead of bending stiffness:

BCT = 5.87 x ETC x √(caliper of combined board x box perimeter)

It provides accuracy close to the original equation and is easier to use, both in testing and mathematically. McKee's work was based on averages. Individual boxes will vary above and below the predicted value. The ability to predict the compression strength of a container is a considerable tool, but it is even more powerful to take a compression requirement, back out an ECT requirement and use it to determine appropriate board combinations. Solving for Ea, the simplified McKee formula is:

ECT = BCT ÷[5.87 x √(caliper of combined board x box perimeter)]

DISTRIBUTION ENVIRONMENT AND CONTAINER PERFORMANCE

The ability of a container to perform in distribution is significantly impacted by the conditions it encounters throughout the cycle. Some of these conditions are difficult for the packaging engineer to influence, including stacking time and relative humidity. Others are determined by handling and unitizing packages; for example, pallet patterns, pallet overhang, pallet deck board gaps and excessive handling. We can now estimate the impact of these conditions on container strength. If the original box compression strength is known (determined in the lab using a dynamic compression tester), we can factor it by generally accepted multipliers to arrive at an estimated maximum safe stacking strength.