We often get asked how to cope with setting the shipping rates where both the dimensions and the actual weight of the product affect the cost. This is in addition to other criteria such as destination, cart total, etc.

Dealing with dimensional weight is not a simple problem, there are often many questions such as:

1. How are the items packed when there are multiples (do all the dimensions get added up, or are larger boxes/pallets used)?
2. Do Dimensionally large items ship together or separately? If so under what conditions?
3. What box sizes are used with what combinations of products

If you are using live rates such as UPS,Fedex, USPS then the WebShopApps Dimensional Shipping extension is in most scenarios a good solution.

If you are using custom based rates that you are defining yourself then I recommend 1 of 4 approaches:

Solution 1 – Premium Rates with Volume Support

The base Premium Rates extension supports setting up rules to filter based on weight and volume.  The extension adds in a volume attribute, which can then be set on the products much as you set weight. You have the choice whether to use the volume weight and/or actual weight, or the higher of the two.  This is a relatively simple solution, but seems to work well for a lot of our Australian clientele where volume is often a factor.

Solution 2 – Product Matrix with Shipping Groups

With the Product Matrix extension you can assign products to shipping groups. So you could say have groups called SMALL, MEDIUM, LARGE.  You can then assign products to one of these groups, and define the rates based on the group. So small items could be $5, large could be $50.  You also have flexibility to say whether this is per item, per order, etc for each group.

Solution 3 – Product Matrix with Volume Support

If you know the dimensions of your products you can look at using Productmatrix with Volume Support and filtering based on weight and volume.  You enter in the width, length, height for each product, then the extension will multiple these with a configurable ‘multiplier’ to get a volumetric weight.  Each of the volumetric weights are added together for the items in the cart (much as you do with standard weight) and shipping rates can then be setup so that they alter based on the actual and/or volumetric weight, plus the shipping group if required.

By using the shipping group you can enforce that different groups are effectively different packages, so for example if you had say items from SMALL and MEDIUM groups in the cart you can set it up so that the SMALL shipping rate is added to the MEDIUM shipping rate.

This is a good solution where you are prepared to invest the time inputting these dimensions for each product (this can be done in a product import as are just attributes), but not so good if you dont know dimensions/weight.

Some of our clients will use shipping groups and volumetric weight, e.g. items in the shipping group table with a volumetric weight of <10lb ship for x price.

Solution 4 – Dimensional Shipping

Potentially your third option is to integrate into our Dimensional Shipping extension and then build custom rates based off the calculations it returns. This is a complex approach, suited to scenarios where you may have items shipping separately and multiple box sizes. It would be custom work to implement such a solution, we would recommend you email us to discuss further.