If the customers are ordering multiple products, and the weight increases, how can I ensure the shipping rate reflects accurately? I want to make sure that shipping price is the sole responsibility to customers, and I am not paying any adjustments.
Great question! Shopify provides the ability to offer calculated shipping rates from a range of shipping providers. If you are using calculated rates at the checkout these rates would scale based on total order weight and the default package size you have set for your shipping.
This does leave some room for adjustments on your end though as the default package size can only be set using one package size. So if the packaging requirements need to be increased, the order’s shipping value may not increase to match appropriately.
You can checkout the supported carriers for Shopify Shipping here: Shopify Help Center | Calculating shipping rates.
If you wish to provide more detailed shipping rates for your customers you may want to look into upgrading your plan to get access to Carrier Calculated Shipping (Third Party) and use an app like Boxify to scale your shipping packages with your items.