Shipping cost depends on how much space your box takes up, not only on what it weighs, and once orders get big enough the rules change completely. Here is one illustrative ceramics shop worked through both: parcel dimensional weight for single orders, and freight class for a wholesale pallet.
| Carrier | Divisor | Rounding of sides | Applies | Size and weight limits |
|---|---|---|---|---|
| UPS Daily Rates (Retail: 166) | 139 | Nearest inch | Every package | 150 lb; 108 in long; 165 in length plus girth |
| FedEx | 139 | Nearest inch | Every package | See the FedEx Service Guide |
| USPS Priority Mail, Ground Advantage | 139 | Up to the next inch | Only above 1,728 cubic inches (1 cubic foot) | 70 lb; oversized price above 108 in length plus girth, up to 130 in |
Dimensional weight is length × width × height ÷ divisor, rounded up to the pound, and you pay the greater of that or the actual weight. USPS moved to the 139 divisor in its July 12, 2026 Domestic Mail Manual revision. For pallets, LTL carriers use the National Motor Freight Classification; since July 19, 2025 most density-rated items follow NMFTA’s 13-tier scale from class 400 (under 1 lb per cubic foot) to class 50 (50 or more).
| Product | Shipping box | Actual weight | UPS billable | FedEx billable | USPS billable |
|---|---|---|---|---|---|
| Mug set (two mugs) | 10 × 8 × 6 in | 4.2 lb | 5 lb | 5 lb | 5 lb |
| Ceramic planter | 14 × 14 × 12 in | 6.5 lb | 17 lb | 17 lb | 17 lb |
| Wall clock | 18 × 18 × 4 in | 3.1 lb | 10 lb | 10 lb | 4 lb |
| Table lamp | 20 × 12 × 12 in | 5 lb | 21 lb | 21 lb | 21 lb |
The mug set is small and dense, so everyone charges its actual weight. The other three are mostly air: every carrier bills the planter at 17 lb, more than two and a half times its 6.5 lb. USPS charges the wall clock (1,296 cubic inches) by its actual weight because the box is under 1 cubic foot, while the planter and lamp, at 2,352 and 2,880 cubic inches, are dimensional with every carrier.
Taking one inch off each side of a box removes a lot of volume, because the change multiplies across all three dimensions:
| Product | Current box (UPS) | One inch smaller each way (UPS) | USPS current | USPS smaller |
|---|---|---|---|---|
| Planter | 14 × 14 × 12 in: 17 lb | 13 × 13 × 11 in: 14 lb | 17 lb | 14 lb |
| Table lamp | 20 × 12 × 12 in: 21 lb | 19 × 11 × 11 in: 17 lb | 21 lb | 17 lb |
A planter box of 13 × 13 × 11 inches is 1,859 cubic inches, 21% less than 14 × 14 × 12, and the billable weight drops by about the same proportion. For USPS the target is clearer still: a box at or under 1,728 cubic inches is billed by actual weight. One trap: UPS and FedEx round each side to the nearest inch, USPS always up, so a box measured at 12.4 inches counts as 12 for UPS and FedEx but 13 for USPS.
A garden store orders 24 planters. On a 48 × 40 inch pallet, the 14 × 14 inch boxes fit 6 to a layer; four layers plus a 6-inch pallet stand 54 inches tall. With an assumed 45-lb pallet the shipment weighs 201 lb in 60.00 cubic feet:
Light, bulky goods like these land in a high class, but as a pallet they are at least priced on real weight and density rather than each box’s dimensional weight.
Density breaks are cliffs. A pallet of 140 mug sets (20 per layer, seven layers, 48 inches tall) weighs 633 lb in 53.33 cubic feet: 11.87 lb per cubic foot, class 92.5. Another 7 lb, a few more mug sets, takes it past 12 lb per cubic foot and into class 85. Removing height has the same effect: the denser the pallet, the lower the class. Measure the pallet as tendered, at its highest and widest points; carriers re-measure with dimensioners and reclassify understated shipments.
Parcel and LTL prices depend on your negotiated rates, zones, accessorial fees (liftgate, residential delivery) and fuel surcharges, so compare actual quotes. For marketplace sellers, remember that eBay and Etsy charge their percentage fees on the shipping the buyer pays too, as shown in eBay, Etsy and payment processing fees compared.
The dimensional weight calculator runs one box through every carrier’s rules and shows the USPS cubic tier; the freight class calculator turns pallet dimensions and weight into density, class and the weight or height that reaches the next class.
Only for parcels larger than 1 cubic foot (1,728 cubic inches) after rounding each side up to the next inch; above that it divides by 139, as UPS daily rates and FedEx do.
Often, for light and bulky goods to one address, because LTL freight is priced on the pallet’s actual weight and freight class rather than each box’s dimensional weight. Compare actual quotes, since fees vary.
150 lb, with a maximum length of 108 inches and 165 inches of length plus girth, according to UPS.
Increase density: build a tighter pallet, avoid overhang and empty space, and combine dense items with light ones where allowed. Each class has a density threshold on the NMFC scale.
Not if the package is already billed by actual weight. Right-sizing helps when the dimensional weight is higher than the actual weight.