Weight based shipping rates


Weight-based shipping rates

Learn how weight impacts shipping quotes.

There are two types of weight that carriers are concerned with when quoting how much it will cost to transport a shipment—physical weight and dimensional weight. Physical weight indicates how heavy a shipment is, while dimensional weight is a calculated value to let carriers know how much space a shipment will take up. Carriers are concerned with both of these weights. Zonos is able to evaluate and use the greater of the two, just as carriers do, to return an accurate shipping cost in your checkout.

Physical weight 

Physical weight can be set at the product level in your ecommerce platform or via Catalog. If you do not know your products' weights, we can estimate them based on the value of the goods in the cart using a feature that is customized to your store, called the igWeightFactor.


The igWeightFactor is used to estimate the weight of an item so that we can return a quote for the cost of shipping even if the true weight of an item is unknown. When we quote shipping costs on an order where a physical weight was not provided, we multiply the value of the order by your igWeightFactor to estimate the weight of the order. While shipping costs will not be as accurate when using an estimated weight as they would be if a true weight was provided, adjusting the igWeightFactor to your store allows us to provide a more accurate and educated estimate.


If an account has an igWeightFactor of .08 (the default), Zonos would estimate a cart with a 300 USD item to weigh 24 lbs. We would then return the shipping rate for a 24 lbs shipment.

300 USD x .08 = 24 lbs

Customize your igWeightFactor

To calculate a custom igWeightFactor for your store, divide your average order weight (in lbs) by your average order value (in USD).

Find your custom igWeightFactor: Use the average order weight (in lbs) / average order value (USD)

Once you know what your custom igWeightFactor is, share it with your onboarding Project Manager or Zonos Support so they can adjust it for your store.

Dimensional weight 

Dimensional weight is a calculated value used by carriers to understand how much space a shipment will take up. It impacts shipping costs when it is greater than the physical weight. A good example of when dimensional weight is greater than physical weight could be a light fixture—something that takes up more space than its weight would normally suggest.

How it is calculated

Dimensional weight is calculated by multiplying the length, width, and height, then dividing by a dimensional divisor (DIM divisor). Standard DIM divisors are 139 for international shipments and 166 for domestic shipments (when the dimensions are in inches), but these can vary. A higher DIM divisor will lead to a lower dimensional weight, which typically leads to lower shipping costs. DIM divisors can often be found on your carrier agreement.

How to apply dimensional weight in your shipping quotes

If dimensional weight is relevant to your business, providing dimensions for your items will allow us to calculate more accurate shipping costs. Some platforms will pass item dimensions to Zonos if you have them included in your product listings. You can also use Catalog to store your item dimensions so they can be used in our calculations.

Ultimately, carriers will want to know how much space your shipment will take up, and that is driven more by the size of your shipping box than the size of your items. If dimensional weight is relevant to your business, and if your shipping boxes take up significantly more space than your items alone, it may be beneficial to calculate shipping rates based on the dimensions of your shipping boxes. You can accomplish this by setting up cartonization.

If physical weight is always greater than dimensional weight, then dimensional weight may never make an impact on shipping costs. In that case, you may decide to not provide dimensions for your products, as they may be irrelevant to shipping costs.

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