
When it comes to air shipping, both weight and size are important parameters when determining the shipping cost. Cargo planes have very limited space, and the payload has a direct impact on the fuel to be consumed for the flight. As a result, logistics companies developed a formula to determine a package's " dimensional weight", which is to be considered in conjunction with the package's actual weight, and the final shipping cost will be based on the higher of the two numbers.
Dimensional Weight =  L(in) × W(in) × H(in) 
139 
• 
The dimensional weight of a package is determined by the product of its length, width and height (in inches) divided by a constant set by the logistics company (currently 139), rounded up to the nearest integer. As illustrated above, for irregularly shaped packages, the dimensions of the smallest possible imaginary rectangular cuboid in which the actual package will fit are used to calculate the dimensional weight.
Please notice that all packages are measured on a precision optical station before shipping, so make sure that you do not squeeze the package in any particular direction before taking the measurement. For example, if the package is bulging a little and the length is 12.3 inches. You see that when you apply some pressure on the sides of the box the length can be reduced to 12 inches and report just that. But remember there will be no 'helping' hands to squeeze the box for you when the logistics company takes the measurement optically, and therefore this dimension is almost always guaranteed to be 13 inches (12.3 rounded up to the next integer) on the actual bill.
Also, please pay attention to anything that may stick out from the edges of the box (labels, package tapes, etc.) as they may block the laser beam and result in a measurement larger than what the box really is. If you pay attention to these details in measuring your packages, most dimensional weight related billing surprises can be avoided.

•  Again, all dimensions are rounded up to the nearest integer before they are used in the formula to calculate the dimensional weight. 
•  The actual weight of the package is also rounded up to the nearest integer. 
•  Special Notice:
A lot of customers use boxes that have dimension numbers printed on them. They simply copied those numbers when creating the shipment, only to find out that, later on, they were charged for overweight because the reported dimensions are smaller than the values measured by the logistics company. In our experience, most dimensions printed on these packaging boxes are simply an approximation. To make matters even more complicated, the actual dimensions of a box also depends on wheter the box was closed and taped properly along all edges. The dimensional weight can differ by quite a few pounds even if the measurement of each side is only off by 1 inch. Please take a look at the following example.
Cleared marked 10×6×6 on the box, the width measures 6.375 in. It is the measurement that counts, not the label. 
Height also measures 6.375 in. This box was properly closed and taped together, it is larger than the marked size by design. 

Box marked as 18×12×6, but the width measures 12.375 in. Logistics company will consider this dimension 13 in, after rounding up. This discrepancy comes from the design of the box, not the way it is closed or taped. It is important that all boxes are actually measured for the most accurate dimension values. 
Again, it is extremely important to obtain the most accurate measurement of you packages' dimensions before creating your shipment. In particular, do not trust the dimensions printed on the box, as they are usually incorrect. It may be hard to believe, but this also applies to boxes provided by the logistics companies themselves. Most of the time, the actual dimensions are slighly larger than what was printed on the boxes. Make sure you measure the boxes yourself and round them up to the next integers.
In fact, as long as the weight and dimensions are carefully measured, it is seldom, although still possible, that the logistics company would report different numbers on the bill as their system is quite accurate. Of course, if the customer feels strongly that the numbers reported on the bill are inaccurate, MeiMei Express will be happy to file a dispute on the customer's behalf. 
