Packaging weight is determined by two methods:

Cubic inches Method.
Mutiply the length x the width x the height. Divide that by 166 and that is the cube weight. (All sizes must be rounded to the next inch)

Weight method:
The scale weight, rounded to the next full pound.

The higher of these two methods will determine the weight used for shipping
This is an industry standard for air freight and is how we are charged.

Remember, a lamp shade weighs almost nothing, but is expensive to ship because of its cubic in volume Weight.