Dimensional weight is a calculation of a theoretical weight of a package. This theoretical weight is the weight of the package at a minimum density chosen by the freight carrier.
*From Wikipedia
Why It Matters
Shipping costs have historically been calculated on the basis of gross weight in kilograms or pounds. By charging only by weight, lightweight, low density packages become unprofitable for freight carriers due to the amount of space they take up in the truck/aircraft/ship in proportion to their actual weight. The concept of dimensional weight has been adopted by the transportation industry worldwide as a uniform means of establishing a minimum charge for the cubic space a package occupies. In fact, UPS and FedEx both announced that starting 2015, shipping charges on all shipments (air and ground) will be determined by greater of the actual weight and dimensional weight of a package. Prior to this announcement, dimensional weight charges were only applicable to packages of a specific size range.
How It's Calculated
Dimensional weight is a calculation of a theoretical weight of a package. This theoretical weight is the weight of the package at a minimum density chosen by the freight carrier. If the package is below this minimum density, then the actual weight is irrelevant as the freight carrier will charge for the volume of the package as if it were of the chosen density (what the package would weigh at the minimum density). Furthermore, the volume used to calculate the dimensional weight may not be absolutely representative of the true volume of the package. The freight carrier will measure the longest dimension in each of the three axis (X, Y, Z) and use these measurements to determine the package volume. If the package is a right-angled rectangular box, then this will be equal to the true volume of the package. However, if the package is of any other shape, then the calculation of volume will be more than the true volume of the package.
Dimensional weight is also known as DIM weight, volumetric weight, or cubed weight. Freight carriers utilize the greater of the actual weight or dimensional weight to calculate shipping charges. Dimensional weight is calculated as (length × width × height) / (dimensional factor). Measurements can be made all in inches or all in centimeters, but the appropriate shipping factor must also be used.
Shipping factors for imperial measurements represent cubic inches per pound (in3/lb) while metric factors represent cubic centimeters per kilogram (cm3/kg). These are the inverse of the package density. Dimensional weight is applied when the actual product density is less than the minimum density represented by the chosen factor. Dimensional weight is representative of the weight of the package at the minimum density accepted by the freight carrier. Shipping factors are not only different for imperial and metric measurements, but also for shipment mode and in some cases between different customers. Shipping factors will be available from the freight carrier. Some common factors are listed below.
Imperial shipping factor examples:
- 139 in3/lb = 12 lb/ft3
- 166 in3/lb = 10.4 lb/ft3 - common for IATA shipments
- 194 in3/lb = 8.9 lb/ft3 - common for domestic shipments
- 216 in3/lb = 8.0 lb/ft3
- 225 in3/lb = 7.7 lb/ft3
- 250 in3/lb = 6.9 lb/ft3
Metric shipping factor examples:
- 5000 cm3/kg = 200 kg/m3
- 6000 cm3/kg = 166.667 kg/m3
- 7000 cm3/kg = 142.857 kg/m3
When calculating the dimensional weight with metric measurements, the length, width, and height are measured in centimeters (cm) and the result is stated in a nominal kilogram (kg) dimensional weight band (usually rounded up).