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Understanding the Shipping Calculator

Different shipping providers and the services they offer have different weight and dimension limits. If these limits are exceeded, the quote can fail, or include extra fees or charges.

Before we can start troubleshooting faulty or missing real-time quotes, we need a basic understanding of how our system calculates the size and weight of a shipment.


How Shipments are Calculated

There are two important key points to know about the BigCommerce shipping calculator:

  • 1. Shipments are calculated as if every item in the order is going into a single box, or as if every item is being packed individually (UPS and FedEx, only).

There is one exception to this rule. If an item in the order has a product-level fixed shipping cost, then the weight and dimensions of that item are not included when requesting a real-time quote.

  • 2. Our shipping calculator stacks items in a single column.

This is where the Factoring Dimension in your store’s Physical Dimension Settings becomes important. If it is set to Product Depth, for instance, then the dimensions for the single box that the shipping calculator is going to build for all the items in the order is determined like this:

  • Width — Maximum width out of all products in the order
  • Height — Maximum height out of all products in the order
  • Depth — The sum of all depths of the products in the order when added together

Diagram representing Width, Height and Depth

Typically, the narrowest dimension between width, height and depth should be set as the Factoring Dimension, and all products should be consistent (e.g. depth is always the narrowest side).


Pro Tip! If you need more advanced shipping functionality, ShipperHQ may be able to help. Check it out in our app store for a full listing of its features.


Example Scenario

A merchant has a music store and sells two products, records and compact discs (CDs). The size and weight of each product is as follows:

  • Records measure 10” x 10” x 1” (Width x Height x Depth) and weigh 0.2 lbs.
  • CDs measure 5” x 5” x 1” and weigh 0.1 lbs.

A merchant receives an order for 2 records and 12 CDs.

Applying the rules we learned in the previous section, this is how the shipping calculator determines the size of the box to be shipped. In this case, we’ve adjusted our UPS and FedEx settings to include all items in the order in one box.

  • The largest width is the records, so that’s 10” for width.
  • The largest height is also the records, so that’s also 10” for height
  • The summed up depth of all the products is 14”.
  • (2 records at 1” each, plus 12 CDs at 1” each)
  • The summed up weight of all the items is 1.6 lbs.
  • (2 records at 0.2 lbs each, plus 12 CDs at 0.1 lbs each)

So the resulting package measures 10” x 10” x 14” and weighs 1.6 lbs. The inside of the package looks like this - notice that most of the box is empty space:

User-added image

A human, or a more advanced shipping calculator would know that we could create 4 columns of CDs on top of the records to make a box that doesn’t need to be so deep.

User-added image

In this configuration, the box is 10” x 10” x 5”, and would result in a lower quote. In both of these cases, the dimensional weight (also known as cubic or volumetric weight) of the package would be greater than its actual weight.

This is a mild scenario - as you can imagine, the more the sizes of the products in the order differ from each other, the more likely it is there will be empty space when the box is calculated, making it unnecessarily large and causing a higher quote.

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