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Weigh the stack first, then keep it flat. A stack of papers mailed unfolded in a large flat envelope stays in the cheaper flat-rate category until it crosses the thickness or weight limit, at which point it gets priced as a parcel and the cost jumps. The cheapest option is almost always the flattest package that still qualifies as a flat: no box, no bubble mailer, no folding.
Postal pricing has categories, and the category is decided by shape, not just weight. A "large envelope" or flat is flexible, uniformly thick, and under the maximum thickness (three-quarters of an inch for USPS). Anything rigid, lumpy, or thicker gets reclassified as a parcel, and parcel pricing starts higher and climbs faster with weight. This is why the same 200 pages can cost noticeably different amounts depending on how you pack them: flat in a rigid mailer they are a flat; in a box they are a parcel.
The non-obvious trick: thickness is measured at the thickest point. A stack with a paperclip bulge, a folded corner bunching up, or a USB drive tucked inside can push an otherwise flat mailer over the limit. Keep the stack clean and uniform, and you stay in the cheaper lane.
| How you pack it | Likely category | Why |
|---|---|---|
| Stack flat in a large manila envelope | Large envelope / flat | Flexible, uniform thickness; cheapest per ounce in this range |
| Stack in a rigid flat mailer | Large envelope / flat (if under thickness limit) | Rigid is allowed as long as it stays flat and thin |
| Stack in a small box | Parcel | Box shape is automatically parcel pricing |
| Stack in a padded bubble mailer | Often parcel | Lumpy and thick; frequently fails the flat tests |
| Pages folded into a standard envelope | Letter (if it still qualifies) | Cheapest of all, but only works for small stacks |
Sometimes. Postage climbs with weight, and two lighter flats can occasionally cost less than one heavy parcel, but usually not: you pay the base price twice. Splitting makes sense when the stack is just over a breakpoint, for example when removing twenty pages drops the piece back into a cheaper weight step. It also makes sense when the recipient does not need everything at once, or when you want to reduce the risk of the whole thing going missing in one package.
Do the arithmetic honestly before splitting. Two mailings means two envelopes, two postage payments, and twice the handling. For most stacks, one well-packed flat beats two thinner ones on total cost.
If the papers exist as files, the cheapest move of all is to not mail your printed stack: have it printed and mailed for you. LetterAgent prints letters on 8.5x11 paper, single-sided, with the page count verified up front, so a thick document goes out as a proper mailed piece without you buying envelopes, weighing anything, or standing in line. You approve the exact quoted price before anything is sent. This is the route people pick for contracts, application packets, and multi-page letters where the printing and packing would take an afternoon.
The one limit to know: LetterAgent mails letters, not parcels, and there are no inserts. A stack of papers that is really a bound report with tabs and dividers is a parcel job; a stack of papers that is really a long letter is a LetterAgent job. If what you have is pages of a document, it fits.
Flat mailers go through sorting machines, and a thick stack can shift, curl, or tear the envelope. Use a rigid mailer (the kind with stiff cardboard) rather than a flimsy manila envelope for anything over about fifty pages. Tape the flap, not just the clasp: clasps pop open in machinery. And write "DO NOT BEND" on both sides. It is not a formal handling instruction the post office guarantees, but handlers do respect it when they see it, and it costs you nothing.
In Canada, the same logic holds with Canada Post's lettermail bands: keep the piece within the oversize lettermail dimensions and weight, or it tips into parcel rates. The flattest compliant package wins in both countries.
Ready to mail it? Send your letter with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and it is printed and mailed.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
Need help? Ask your assistant: it can check a job's status any time. If it ever can't handle something: hello@getletteragent.com