What Is Dimensional Weight and How to Calculate It

What Is Dimensional Weight and How to Calculate ItYou probably know that most shipping carriers charge for weight: the heavier the package, the more it costs to ship. However, shipping costs aren’t always calculated on the basis of gross weight. Some carriers charge by the so-called dimensional weight when shipping lightweight, low density packages. What is dimensional weight and how to calculate it?

Gross weight is the combined actual weight of the parcel contents and packaging. It doesn’t need to be calculated, all you have to do in order to learn the gross weight of a parcel is place it on the scales. In contrast, dimensional weight is a theoretical (estimated) weight that is calculated from the dimensions of a package, hence the name.

Shipping costs have historically been calculated on the basis of real weight, but at some point shipping lightweight packages became unprofitable for carriers because they take up too much space in proportion to their actual weight. To solve this problem, shipping carriers worldwide adopted the concept of dimensional weight.

Dimensional weight, also known as DIM weight, cubed weight or volumetric weight, is calculated from the length, width and height of a package. If the dimensional weight of a package is bigger than its actual weight, you will be most likely charged by weight, although some carriers apply DIM weight charges only to packages of a specific size range.

Generally, volumetric weight is calculated as package length multiplied by height multiplied by width and divided by dimensional (shipping) factor, also known as volumetric divisor. Shipping factors are different for imperial and metric units (i.e. inches and centimeters), shipping carriers and in some cases shipment modes. Here is how to calculate dimensional weight for some carriers.


The United States Postal (USPS) Service applies DIM weight pricing domestically to Priority Mail, Priority Mail Express, and non-lightweight Parcel Select parcels larger than a cubic foot. The USPS uses 166 as a volumetric divisor for domestic packages, so to calculate DIM weight you need to multiply your package’s length by width by height (all dimensions in inches) and divide the resulting number by 166.

As far as international shipments are concerned, the USPS mostly uses flat rate pricing so there’s no need to weigh your parcel or calculate its dimensional weight unless the parcel exceeds weight or size limits. With flat rate, you pay one rate depending on the destination country.


FedEx uses the imperial system to calculate dimensional weight so you need to multiply length by width by height in inches and divide the resulting number by 139 (FedEx applies the same shipping factor to U.S. and international shipments). Then compare the dimensional weight and actual weight of the package (in pounds). Shipping charges will be determined by greater of the two.


UPS (United Parcel Service) uses the concept of billable weight to calculate the shipping rate. For both domestic and international shipments, the billable weight is the greater of the actual (gross) weight and the dimensional weight. To determine the package dimensional weight, multiply length by width by height (all dimensions in inches) and divide the resulting cubic size by 166 for Retail Rates.

When determining the package dimensions, round each measurement to the nearest whole number (for example, 1.00 to 1.49 is considered 1, and 1.50 to 1.99 is considered 2). When determining the dimensional weight, increase any faction to the next whole number.

When calculating the shipping cost with the PostageMaker shipping calculator, please indicate the right weight of your parcel. For this, you need to determine its actual weight and dimensional weight, and then choose whichever one is greater for shipping cost calculations.