Dimensional weight (also called DIM weight or volumetric weight) is a pricing method that charges a shipment based on the space it takes up rather than only its actual scale weight. Carriers bill whichever is greater — actual weight or dimensional weight — because a large, light box uses cargo space that a small, heavy box does not.
If you ship bulky-but-light products (pillows, lampshades, plastic housewares), DIM weight is often what drives your bill. Understanding it is the fastest way to cut avoidable freight and parcel costs.
The dimensional weight formula
The standard formula is:
DIM weight = (Length × Width × Height) ÷ DIM divisor
Measure the package in inches, multiply to get cubic inches, then divide by the carrier’s DIM divisor. Common divisors are 139 for domestic parcel (UPS/FedEx) and 166 for some international and USPS services; freight carriers use different density rules.
Example
A 20″ × 18″ × 12″ box = 4,320 cubic inches. Divided by 139 = about 31 lbs of dimensional weight. If the box actually weighs 12 lbs, you’ll be billed as 31 lbs because DIM weight is greater.
DIM weight in LTL and freight
For LTL freight, density (pounds per cubic foot) feeds directly into the NMFC freight class that determines your rate. Low-density freight lands in a higher, more expensive class. Calculating density before you book lets you classify accurately and avoid reclassification fees and surprise re-bills.
How to reduce dimensional weight charges
Right-size your packaging so there is little empty space; oversized boxes inflate DIM weight. Use the smallest box that protects the product, minimize void fill, and consider whether items can ship disassembled. Consolidating multiple small parcels into one optimized carton or palletizing for LTL can also lower total cost. A 3PL that handles pick-and-pack fulfillment can standardize carton sizes to control DIM weight across every order.
Frequently asked questions
Why do carriers use dimensional weight?
Trucks, planes, and vans run out of space before they run out of weight capacity. DIM weight ensures shippers pay for the cubic space they actually consume.
What is a DIM divisor?
A number set by the carrier that converts cubic inches into a billable weight. A higher divisor (e.g., 166) yields a lower DIM weight than a lower divisor (e.g., 139).
Does DIM weight apply to pallets?
Freight pricing uses density and freight class rather than a parcel DIM divisor, but the principle is the same: low-density, space-hungry pallets cost more.
Stop overpaying on light, bulky freight
Go Freight’s AI-powered, asset-based Miami operation optimizes packaging, class, and routing so you pay for what you actually ship. Get a quote or call (786) 445-0150.