How do I charge shipping based on the number of items in the shopping cart instead of just a flat fee?
This is a question that is asked by both new and experienced WooCommerce shop owners and the answer is very simple and doesn’t even involve a plugin. Here’s how:
In the Woocommerce Dashboard, under WooCommerce > Settings > Shipping, you can add any number of advanced costs such as quantity-based costs or additional fees, to your flat rate shipping. To charge users per item in your cart, all you have to do is include the item quantity in your shipping cost formula with the [qty]
shortcode:

Adding 3*[qty] means that instead of charging $3 per order, the user will be charged $3 per every item in their shopping cart. Pretty nifty huh.