The last common “three-stamp” letter step
At 3 billable ounces, many machinable letters line up as one Forever + two additional-ounce stamps—three stamps total—before surcharges. This page is for mail that still qualifies as a letter under the tool’s limits, not for flats or parcels.
When 3 oz letter pricing applies
Use this flow when your sealed weight rounds to 3 oz, the piece fits letter dimensions and thickness, and the calculator does not switch you to large-envelope pricing. Invitation suites, thick greeting cards, and multi-sheet packets are common real-world fits—as long as they stay under the letter weight cap.
Example scenarios
Three ounces shows up often in real mail. A wedding invitation with a reply card and liner can land near three ounces once sealed. A short report with a cover sheet and a few folded pages may do the same. Photo greeting cards on heavy stock, small catalogs, and thick holiday cards also reach this weight when the envelope is packed. Tax packets, school forms, and job applications with multiple sheets are other examples. If you expected only 1 oz letter postage or 2 oz, re-weigh after everything is inside the envelope. In each case the question is the same: does the piece still qualify as a standard letter for size and thickness, and what does the ounce ladder cost after rounding?
Common mistakes
People sometimes use the weight on the scale without rounding up. Letter retail pricing in this calculator uses whole billable ounces, so a reading like 2.4 oz becomes three ounces for postage. Another mistake is forgetting the non-machinable surcharge when the envelope is square, rigid, or lumpy. That surcharge is separate from the ounce stamps; it is not the same as buying one more additional-ounce stamp. A third mistake is assuming that three ounces of contents always stays a letter. If the sealed piece is too thick, too large, or over the letter weight cap, the mail may be a large envelope. Letter stamp counts from a three-ounce table do not apply to flats.
How 3 oz stacks on this letter ladder
For a machinable 3 oz letter, this model charges the first-ounce rate once, then two additional-ounce increments—shown as separate lines before any non-machinable surcharge. The 3.5 oz letter cap means 3 oz still fits; at 3.6 oz rounded you may be in four-ounce territory or out of letters entirely—watch the calculator’s letter-vs-flat message, not just the ounce count.
Additional ounce stamps at three ounces
At three billable ounces, retail letter math usually means one stamp covers the first ounce and two additional-ounce stamps cover the second and third ounces. That is three stamps total for a plain rectangular letter with no surcharge. The Forever stamp pays the first ounce at the current letter rate. Each additional-ounce stamp pays one step on the additional-ounce ladder. If a surcharge applies, you still need enough total postage to cover the surcharge line in the breakdown, which may mean extra stamps in mixed denominations or postage printed online. If your sealed weight goes above 3.5 ounces or the piece fails letter limits, stop using three-ounce letter logic and follow the flat or retail guidance the tool describes.
Before you mail
Weigh after you seal. Tape, wax seals, and clasps add weight. If you sit just under the letter weight limit, small changes can push you into the next ounce or out of the letter class. When the mail is important, checking the numbers twice beats postage due on delivery.