The below will explain how the system calculates weights for shipping of stock items with relationship items.

This will depend on the type of relationship the stock item is using. We have listed both scenarios below.

For a stock item with a Build relationship, only the weight of the parent item is considered and the individual weights of each child item is ignored.

For stock items with a Move With relationship, the weight of the parent items in addition to the weight of each component is considered. If your parent item weight is the same as the sum of its components we would suggest leaving it's average weight as zero otherwise just give a weight to account for the difference between the total relationship weight and the weight of all child items.