All major carriers have shifted to charging by "shipping weight" which is defined as "the greater amount between either the package's dimensional weight or its actual weight." The dimensional weight is calculated as:
[ length x width x height ] / DIM divisor where each dimension is rounded to the nearest whole number
The DIM divisor varies from carrier to carrier. The merchant is responsible to know what are the dimensions of his usual shipping container and the DIM divisor for the carrier he is using for his shipments in order to properly set the shipping costs in each of his Shipping Zones.
- USPS -- DIM divisor: 166 (dimensions are measured in cubic inches)
- FedEx -- DIM divisor: 139 (dimensions are measured in cubic inches), 5000 (in cubic cm)
- UPS -- DIM divisor: 139 (dimensions are measured in cubic inches)
- Canada Post -- DIM divisor: 139 express/ 166 standard (in cubic inches), 5000 express/6000 standard (in cubic cm)
Calculating the actual "shipping weight"
- Example 1 -- An item measures 100 cm x 60 cm x 20 cm with an actual weight of 8 kg. Based on the parcel's dimensions, its volume is 120,000 cm3. If it were shipped using Canada Post Express service, a density factor of 5,000 would apply resulting in a volumetric equivalent of actual weight of 24. Because the volumetric equivalent of actual weight of 24 is greater than the actual weight of 8 kg, the correct shipping charge is based on volumetric equivalent of 24 kg.
- Example 2 -- An item measures 100 cm x 60 cm x 20 cm with an actual weight of 26 kg. Based on the parcel's dimensions, its volume is 120,000 cm3. If it were shipped using Regular Parcel service, a density factor of 6,000 would apply resulting in a volumetric equivalent of actual weight of 20. Because the actual weight is greater than the volumetric equivalent of actual weight, the correct shipping charge is based on actual weight of 26 kg
