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This article applies to selling in: United States

Dimensional weight

Definition Dimensional weight is a calculation of the volumetric weight of a package, using the package’s length, width and height.
Using this article Dimensional weight is used to determine your item’s product size tier and shipping weight in certain instances. After reading this article, you will be able to (1) determine whether dimensional weight is used to calculate fees for your item and (2) calculate the dimensional weight for your product. To accomplish these tasks, you should first know the unit weight, product volume, and product dimensions.
Fees that use this attribute

FBA fulfillment fees

Monthly inventory storage fees

Long-term storage fees

FBA inventory storage overage fees

FBA removal order fees

FBA disposal order fees

Fulfillment fees for Multi-Channel Fulfillment orders

FBA Inventory Placement Service fees

FBA Prep Service fees

Related terms and articles

Product dimensions and volume

Shipping weight

Product size tier

Unit weight

FBA fees reimbursement policy: Weight and dimensions

Determine if dimensional weight is used to calculate fees

Dimensional weight may apply when calculating fees for items that meet either of the following criteria:

  • The item is standard-size and weighs more than 0.75 pounds; or
  • The item is oversize, but not considered special oversize.

Use the dimensions and unit weight to determine if the item is standard-size or oversize.

A standard-size item is one that meets all of the following criteria when fully packaged:

  • Unit weight is less than or equal to 20 pounds
  • Longest side (length) is less than or equal to 18 inches
  • Median side (width) is less than or equal to 14 inches
  • Shortest side (height) is less than or equal to 8 inches

If a standard-size item meets all of the criteria above and weighs more than 0.75 lb, the greater of dimensional weight or unit weight is used to calculate fees. If the item weighs 0.75 lb or less, only unit weight is used instead.

Items that do not meet the standard-size criteria above are considered oversize. A special oversize tier applies to products that must be delivered using special delivery options due to their size, weight, special handling requirements, or other restrictions. Products are classified and charged as special oversize if any of the following is true:

  • Unit weight is greater than 150 pounds
  • Longest side (length) is greater than 108 inches
  • Girth plus length is greater than 165 inches. To calculate girth plus length:
    • Measure the length, height, and width of the packaged unit.
    • Calculate the girth by adding the shortest and median sides and multiplying by 2.
    • Add the longest side and girth.
  • Amazon has determined that the product requires special handling to ensure a good customer experience

If your item did not met any of these criteria, the greater of dimensional weight or unit weight is used to calculate fees. If it does meet any of the criteria, the item is considered special oversize, and only unit weight is used instead.

Calculate dimensional weight

The dimensional weight is equal to the unit volume (length x width x height) divided by 139. The dimensional weight for oversize items assumes a minimum width and height of 2 inches.

Important: If a product is sold as a set, the weight and dimensions used are the weight and dimensions of the set packaged together.

You can look up product dimensions for your existing FBA inventory using the Monthly Storage Fees report. To do so:


  1. Download the report
  2. Identify the product of interested by its FNSKU
  3. View the Product dimensions in the longest-side, median-side, and shortest-side fields
  4. Use the formula above to calculate the product volume and convert to dimensional weight

For products that are already being sold in Amazon stores but you do not sell, you can look up the product dimensions to calculate volume by using the Revenue Calculator. To do so:


  1. Search for the product of interest
  2. View the Package Dimensions values
  3. Use the formula above to calculate the product volume and convert to dimensional weight

For products you currently have in FBA inventory, you can look up the size tier using the Fee Preview report. To do so:


  1. Download the report
  2. Identify the product of interested by its FNSKU
  3. View the product size tier in the product-size-tier field
Note: Amazon may verify the weight and dimensions of a product using representative samples. Amazon’s information about a product’s weight and dimensions will be used to calculate fees if there is a difference between Amazon’s information and a seller’s information. Amazon may change its information about a product’s weight and dimensions from time to time to reflect updated measurements. Fees based on the weight and dimensions of a product are calculated using Amazon’s information about the weight and dimensions of that product at the time the fee is calculated.

Dimensional weight example

Dimensional weight with a 2 inch minimum

White dry erase board

Dimensions: 40 x 1 x 25 inches

Unit weight: 4.5 lb

Dimensional weight: 14.4 lb, 2-inch minimum applied (40 x 2 x 25 inches, divided by 139)

Item is oversized, but not special oversized, so dimensional weight is used for fee calculations.

Frequently asked questions

Which measurement system does Amazon use to measure products and calculate fees, imperial or metric?

The measurement system for product dimensions and volume vary depending on the local standard in which the fees are calculated. The fee Help content for the region indicates which measurement system and units of measure are used for that region.

How is unit weight different from dimensional weight?

Unit weight is the scale weight of the product when fully packaged. Dimensional weight is an estimate of what the weight will be based on the product’s dimensions. Depending on the size tier of the product, either the unit weight or the dimensional weight will be used to calculate the shipping weight. View more details on the Shipping weight page.

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