Shipping rates are wrong! Too expensive, or not charging enough?

If you notice customers are being undercharged, or overcharged - most of the time, there is configuration issue either in Shopify, Addition or both.

Firstly, how does the app calculate shipping?

The app looks at the products in the customers cart, Shopify will send the app the total weight of the cart. Then the app then needs to figure out, what package it should use to quote the shipping rate.

It will review all the product dimensions to decide if it should use Package A, B or C or a small, medium or large satchel etc. Your packages + product dimensions need to be saved in Addition.  The app will automatically determine both what package to use and how many, i.e. it decides if an order of 100 items for example, will fit into one package, two or even more packages based on those product dimensions.

What to check in Addition:

  • Have you updated your product dimensions? This is crucial information and the only way the app can determine what package to use, to calculate shipping. When you do not update product dimensions within Addition, the app will need to use the fallback measurement which is 5x5x2cm, meaning it can under quote shipping rates.
  • Are the product dimensions too small or too large?  The app uses math logic (LxWxH) to calculate product volume, make sure you don't overestimate the dimensions entered into Addition. 
  • Configure your packages in Addition not in Shopify.
  • Ensure that if the packaging alone weighs 100grams or more, this should be accounted for by adding an 'Empty package weight', especially for international shipping calculations!

What to check in Shopify:

  • The app requires product weight(s), this is managed in Shopify, against your Product settings. Make sure you have assigned the correct weight for your products in Shopify.

The most common errors include no weights at all against products and/or the incorrect weight unit has been selected, e.g. 0.1 g, instead of 0.1 kg


  • Do you have Shipping profiles that are combining rates?  When Shopify Shipping profiles are used, Shopify takes over our calculations and will combine rates for products in different profiles. This can cause an inaccurate shipping rate, combined rates are identifiable as they will be described as "Shipping", rather than the rate name you have set up in Addition e.g. Express Post, or Parcel Post
  • Verify that it is the Addition app providing rates at the checkout. Have you deleted Shopify's default rates or removed outdated flat rate rules that shouldn't be in place? 

What rate are you expecting to see?

If all else fails, reach out to support and provide us with the below information so we can troubleshoot:

  • The names/SKU's of all the items in the cart
  • The total cart weight
  • What package dimensions the order will be shipped in
  • The postcode/country of the customer