Poly Mailer Size Guide: Measure Clothing & Check Cubic

A garment category is not a package dimension. Fold the exact item as it will ship and record length, width, and thickness without crushing loft, structure, embellishments, or hardware. This guide starts with a fit estimate: item width plus thickness for the bag width, and item length plus thickness plus closure room for the bag length. Treat that result as a sample size, not a promise. The finished test package must close across a flat surface without stretching the seam or adhesive strip.

Bag fit and postage are separate decisions. A smaller mailer can reduce material use and may place an eligible commercial Ground Advantage shipment in a lower cubic tier, but postage still depends on the purchased service, zone, weight, package characteristics, and the dimensions sent with the label. Pack one representative order, weigh and measure the sealed parcel, and compare the eligible services in the actual label flow before ordering mailers in bulk.

USPS DMM 283.1.3 and the July 12, 2026 update set the current Ground Advantage Commercial Cubic rules. For an eligible non-pleated soft pack, the original unused mailer must have length plus width of 36 inches or less; the five tiers are 0.10 through 0.50. The parcel must weigh 20 pounds or less, remain at or below one cubic foot, and have no dimension over 22 inches. Pleated or expandable bags use three-dimensional cubic measurement instead of the unused-bag shortcut.

Run a 12-order test before standardizing. Record item type and size, folded measurements, chosen bag, seam and adhesive result, packed weight and dimensions, purchased service, zone, label price, damage or return outcome, and pack time. Reorder the smallest size that closes cleanly and produces the best total cost without damage. Do not annualize a one-order postage difference unless service, zone, weight, and package treatment are comparable.