Packaging: Box Dimension Guidelines
Length x Width x Depth
To determine the propper length, width and depth, place the carton facing you with the opening pointing up (as if the carton was going to be filled from above).
Measure length first:
Open package - the length is the larger of the two dimensions around the open end.
Width is the smallest dimension around the open end.
Depth is the distance between the two ends.
When determining the size of a folding carton, be sure to measure from the middle of the score. To ensure accuracy, measurements should be taken to 1/32th of an inch.
Mailers are measured in a similar fashion to the folding carton, except the mailer only has two dimensions; Width (W) and dimension (D). Width is measured in the horizontal direction while depth is measured vertically.