uShip calculates shipping rates based on several factors:

1. Product Dimensions:
   1. Length, width, and height
   2. Imported directly from your product's title or description
   3. Additional functionality for size variations with Shopify metafields. 
2. Product Weight: The weight specified for each product in your Shopify admin
3. Origin ZIP Code: Your store's shipping origin, set in Settings > Shipping > Shipping origin
4. Destination ZIP Code: The customer's shipping address