One person, doing the arithmetic nobody wants to do by hand.
A paid review of your last 90 days of USPS shipments. You send a CSV export; you get back a spreadsheet listing every parcel that hits a size or weight threshold, the rule it hits, how far past the threshold it is, and the smallest change that clears it.
There are also two free calculators on this site. They answer one box at a time. The audit answers a quarter of shipping at once.
A software engineer, working alone. Not a logistics company, not a 3PL, not affiliated with USPS in any way.
The reason this exists: the rules that decide what a parcel actually bills at are published, precise, and completely unreadable. DMM 601 and DMM 123 are written like legal text, but applying them to a specific box is arithmetic — measure three sides, add them the way USPS does, compare to four numbers. That's a job for a script and a careful eye, not for a seller at 11pm with a tape measure.
Every finding cites the section it comes from, so you can check any line yourself at pe.usps.com:
| Rule | Source |
|---|---|
| Overweight / oversize fee, $200 | DMM 601.1.2.3, as revised by Postal Bulletin 22702 (effective 7/12/2026) |
| 130-inch and 70-lb mailability limits | DMM 601.1.2.1 |
| Balloon pricing, 84–108 in under 20 lb | DMM 253.1.4 |
| Dimensional divisor 139 | DMM 123 (effective 7/12/2026) |
| 1 cubic foot DIM threshold | DMM 253 |
Rules are retrieved and dated. If a rule changes after your report, the report says which version it used.
If a line in your report is wrong, tell me and I'll redo it or refund it. If the report doesn't identify at least one package you should change, it's free.
Email: REPLACE_WITH_YOUR_EMAIL — I answer within one business day.