Shipping carriers in Prestashop can be organized by either weight ranges or price range.  The following Prestashop 1.5 tutorial will show how to set the ranges for your carriers based on weight.

How to set the Shipping Carrier weight ranges in Prestashop 1.5

1. Login to the Prestashop 1.5 Administration Panel as an Administrator
   
2. Go to  SHIPPING in the menu bar hover over it until the drop-menu appears. Select WEIGHT RANGES when it appears.
3. Select the carrier that you need, then click on EDIT to modify.  Create a weight range for a carrier by clicking on the ADD NEW button.
   
   
   
   
4. When creating a new weight range for a carrier, you will see the following screen.  Click on the drop down arrow to select the carrier, then fill in the weight range that you wish to assign
   
   
5. Select the green SAVE button in the top right hand corner to save your entries

Selecting the appropriate weight range allows you to properly organize the carrier that will be most appropriate for your customers when they are expecting to receive products from you.  As with the price range and out-of-range behaviors, the options that the customer will see depends on the products they are trying to ship.  In this case, the determining factor will be weight.  Otherwise, it will be transparent to the user.  They will only see the final sales totals (including the shipping costs) as presented in the customer cart checkout screen in the example below: