You sell boxes of tissues, which are already in boxes. When they are in the cart on their own they should ship using their own dimensions. When there are multiples in the cart, however, they can be packed together and sent as a single package.
To ship using boxes and dimensions the Dimensional Shipping feature must be enabled.
You can mimic this functionality by defining boxes that are fractionally larger than the products’ dimensions.
For example, if the box of tissues is 3x2x3 you can create a box with dimensions of 3.1×2.1×3.1 and assign it as an applicable box for that product. You will need to do the same for any larger boxes that the boxes of tissues would fit into.
This will make it so that when there is one box of tissues in the cart it will ship in the 3.1×2.1×3.1 box. If there is a quantity of 2 or more in the cart larger boxes will be used instead.
Scenario: Shipping with other products
In addition to the boxes of tissues you sell mugs, which are also in their own boxes. When there is one box of tissues or one mug in the cart they should ship in their own boxes respectively. When in the cart together they can ship together in a single box.
Just like the tissue boxes above, the box for the mug will need to have a box defined that is fractionally larger than the dimensions of the mug. In this case the mug is 4x3x4 but we don’t want this box to be used to ship tissues.
To account for this different packing rules will need to be used, one with the 4.1×3.1×4.1 box plus larger boxes for the mug and one with the 3.1×2.1×3.1 box plus larger boxes for the tissues.
Assigning the first packing rule to the mug and the second packing rule to the tissues will make it so that when there is a quantity of 1 of either product in the cart on its own, it will ship in its own box. However, because there are common, larger boxes available to both products they will be packed together when in the cart together.
Verify that your carriers and rules are working and see how they will display in your checkout right from the ShipperHQ dashboard.