Estimating Shipping

I am trying to find a way to estimate shipping through my WordPress admit pages. Normally I sell one product at a time but if someone is wanting more than one item i have to use a different box and the calculations change. I can manually change the shipping after someone has made a purchase but I can not find a page for shipping before hand.
I am going through the USPS website but I’m not finding the information I need.

• This topic was modified 4 years, 4 months ago by Jan Dembowski. Reason: Moved to Fixing WordPress, this is not an Everything else WordPress topic