Some information may be important for you:
Shipping cost is determined by the greater of the actual weight or the dimensional weight (Dim Weight or Volumetric Weight). Actual Weight is the weight of the package when put on a scale. Dimensional Weight is based on the size of the package. Large items that have a small Actual Weight, like pillows and lamp shades, will have a larger Dimensional Weight. Generally, the DIM weight is calculated as follows (in pounds):
DIM weight = (Length X Height X Width) /139