How the size of your box — not just its weight — determines what carriers charge, and how to package shipments so you're never billed for empty air.
Since carriers introduced dimensional (DIM) weight pricing, package size has become as important as actual weight. A lightweight item in an oversized box can cost more to ship than a heavier item in a tightly-fitted one. Sellers who don't account for this routinely overpay without realizing why.
The formula carriers use to convert package size into billable weight, explained with real examples.
Read the guide →The right way to measure length, width, and height for accurate rate quotes.
Read →Case-by-case math on switching from oversized boxes to fitted mailers.
Read →How the divisor number changes your billable weight across USPS, UPS, and FedEx.
Read →A pricing method that charges based on a package's volume, not just its actual weight — used to reflect how much truck or plane space it takes up.
Carriers re-measure and re-weigh packages during transit and will bill any difference, sometimes with a correction fee added.