The buyer doesn't have to do anything, it works completely automatically. You have never seen an eBay listing that requires the buyer to input their ZIP Code in order to figure their postage cost, unless you were not signed in, or had signed in using an account with a non-US Primary address.
As noted in the other post, the way to set up calculated postage in our listing depends on which listing form you're using. In the shipping section of the Advanced version of the listing form (also known as the business tool) look for the drop-down menu that has "Flat: Same cost to all buyers" at the top, and choose "Calculated" instead.
Regardless of which listing form you use, the way calculated shipping works is the same: You enter the package weight and dimensions, choose which service(s) to offer, and then the shipping calculator will automatically do the rest, showing the correct postage cost from our ZIP Code to that of any member who looks at your listing.
