Введение

The question is almost never "what does a stamp cost." It is "what does my envelope cost to send" — and the piece in your hand may price as one of three different things depending on measurements you have probably never taken.

Postal services price envelopes by shape first, weight second. That ordering surprises people, because weight is what they think about. In practice, an envelope that is one eighth of an inch too thick, or slightly too rigid, jumps to a higher price even if it weighs almost nothing.

This guide walks the decision in the order the postal system applies it: measure the shape, test the thickness and rigidity, then weigh it. For choosing a large envelope size in the first place — the purchasing decision — see our большие почтовые конверты guide. That article helps you select a size to control cost; this one starts from an envelope you already have and works out what it will cost to send.

Rates change. Every figure below is dated and attributed. Postal prices are revised periodically, so always confirm against the carrier's current published rates before you mail in volume.

Three Questions That Decide the Price

The system asks three questions in a fixed order.

OrderВопросWhat It Sets
1What shape is it?Letter, large envelope, or parcel
2Is it uniform and flexible?Whether surcharges or upgrades apply
3How much does it weigh?Which weight step within that shape

Answering them out of order is what produces the unpleasant discovery at the counter.

Wrong orderWhat goes wrong
Weight firstYou priced an ounce figure that the shape never qualified for
Size without thicknessThickness quietly pushes the piece up a tier
Ignoring rigidityA stiff envelope prices as a parcel

The Size Test: Letter, Flat or Parcel

Using the United States as the worked example — the structure is similar in most postal systems — the thresholds are:

ФормаMaximum DimensionsMaximum Weight
Письмо11½" long × 6⅛" high × ¼" thick3,5 унции
Большой конверт (плоский)15" long × 12" high × ¾" thick13 унций
ПосылкаLarger than flat limits—

The rule that governs everything: exceeding any one maximum moves the piece to the next shape up.

If the envelope is…It prices as
Within all three letter limitsПисьмо
Over on length, height, or thicknessБольшой конверт (плоский)
Over on any flat limitПосылка
Rigid, though within flat sizeПосылка

Note that "exceeding any one" includes thickness. A #10 envelope that is physically 11½ × 6⅛ but stuffed to a quarter inch and beyond is no longer a letter, however familiar it looks.

Common envelopeФормаПочему
#10, one or two sheetsПисьмоWithin all limits
#10, stuffed thickБольшой конвертThickness exceeded
6×9 with a bookletБольшой конвертLength exceeded
9×12 with documentsБольшой конвертLength exceeded
9×12 with a rigid boardПосылкаЖёсткий

The Thickness and Rigidity Trap

Two properties cause more unexpected upgrades than size and weight combined.

ПараметрThreshold Effect
ТолщинаOver ¼" leaves the letter class
ЖёсткостьA rigid flat-size piece prices as a parcel
ОднородностьLumpy contents can trigger handling surcharges
ФормаFlats and letters must be rectangular

Rigidity deserves emphasis because it is invisible on a ruler. A flat envelope with a stiff backing board, a rigid insert, or contents that will not bend is treated as a parcel even though its dimensions are within flat limits.

СодержимоеЭффект
Paper onlyFlexible — normal treatment
Card or photo with boardApproaching rigid
Rigid mailer or boxПосылка
Small rigid objectParcel, or non-machinable
ТестКак
Flex testCan you bend it slightly without damage?
Thickness testMeasure the loaded piece, not the empty envelope
Uniformity testDoes the surface bulge or step?
Shape testAre all corners square, with no odd protrusions?

The Weight Test and the Per-Ounce Step

Once the shape is settled, weight sets the price within it.

Weight StepКак это работает
First ounceThe base price for that shape
Each additional ounceA fixed increment, often to a ceiling
Over the ceilingMoves to the next shape or service

Two behaviours catch people out. First, the step is not proportional — a letter at 1.1 oz pays the same as one at 2 oz. Second, the increments continue past the letter ceiling: a flexible letter-size envelope heavier than the letter maximum gets priced at large-envelope rates.

ЭлементPriced as
Letter at 1.0 ozLetter, first ounce
Letter at 1.1 ozLetter, second ounce step
Letter at 3.5 ozLetter, at its ceiling
Letter-size at 4 ozLarge envelope rates

Current Rates at a Glance

The figures below are United States Postal Service retail prices effective 12 July 2026, verified 5 October 2026 against the USPS price-change announcement and current rate tables. They are here to show the shape of the pricing, not to replace the carrier's own calculator.

ПараметрТариф
Letter, 1 oz$0.82
Letter, each additional ounce$0.29
Postcard$0.65
Large envelope (flat), 1 oz$1.69
Non-machinable surcharge (letters)$0.49
International letter, 1 oz$1.75
Certified Mail (additional fee)$5.55

Worked examples using those rates:

MailpieceРасчётПочтовый сбор
#10, one sheetLetter, 1 oz$0.82
#10, 1.5 ozLetter, 2nd ounce step$1.11
Square card, 1 ozLetter + non-machinable$1.31
#10, 3.5 ozLetter at ceiling$1.69
9×12, 1 ozFlat, first ounce$1.69
9×12, 2 ozFlat, second step$1.98
Letter-size, 4 ozFlat rates apply$2.56

The square card example is the clearest illustration of shape pricing: it weighs the same as the flat letter above it but costs less, because it stays in the letter class and takes a surcharge rather than moving up a whole shape.

ComparisonПочему
Square card $1.31 vs 9×12 flat $1.69Letter class + surcharge beats a shape upgrade
#10 at 3.5 oz $1.69 = 9×12 at 1 oz $1.69Two different routes to the same price

Six Reasons Postage Jumps a Tier

These are the practical triggers, in rough order of how often they surprise people.

#ТриггерЭффект
1Over ¼" thickLetter becomes large envelope
2Rigid contentsFlat-size becomes parcel
3Non-rectangular shapeNon-machinable surcharge or higher shape
4Hard objects insideRigidity, or parcel treatment
5Window or clasp creating a stepUneven thickness, possible surcharge
6Wax seal, string, or bulky closureНе проходит машинную обработку

The surcharge itself applies to letters only — it does not apply to large envelopes or parcels. That matters because it means a slightly-awkward letter is often cheaper than a clean large envelope.

СитуацияCheaper route
Квадратная открыткаLetter + surcharge
Slightly thick letterReduce contents to stay under ¼"
Rigid flatRethink the packing, not the envelope size

Self-Checking Before You Go to the Post Office

Most overpayments and rejected pieces are caught in two minutes at a desk.

Установите флажокTool
Толщина в нагруженном состоянииRuler, or a slot cut to ¼"
Loaded weightKitchen scale reading in ounces or grams
FlexYour hands
ФормаA straight edge and square corners
ComparisonThe carrier's own online calculator

A kitchen scale is accurate enough for the decision, because the thresholds are coarse — you are looking for which band you are in, not a precise figure.

Weight threshold to watchПочему
3,5 унцииLetter ceiling
13 унцийFlat ceiling
1 ozBase rate boundary

For working in grams and pounds rather than ounces — and for the paper-weight figures that drive the total — see our envelope weight conversion guide. If your contents are sized in millimetres, our таблицу пересчёта размеров конвертов guide handles the unit comparison.

International Mail

International letter pricing is simpler at the base and less predictable above it.

ПараметрRate / Behaviour
International letter, 1 oz$1.75 (USPS, July 2026)
Above 1 ozVaries by destination country
Shape rulesStill apply — size and rigidity matter

Destination-specific pricing means the practical approach is the same as domestic: settle the shape first, then price the weight. Rates also change independently of domestic revisions, so confirm at the time of mailing.

Getting Back Down a Tier

Because pricing is stepped, small changes can move a piece down a whole class.

РычагЭффект
Reduce loaded thicknessLetter instead of large envelope
Remove rigid backingFlat instead of parcel
Fold the contentsFlat contents into a letter-size envelope
Switch to lighter stockLower weight step
Avoid square formatsAvoid the non-machinable surcharge
Reconsider the closureRemove non-machinable features

Folding is the largest single lever, and it is also a design decision rather than a postal one — a folded certificate or artwork may be worth the higher rate.

ПриоритетТогда
Protecting the contentsAccept the higher class
Cost per piece at volumeFold, and use a lighter stock

What This Means for Envelope Specification

For anyone buying envelopes rather than just mailing one, postage belongs in the specification alongside paper and print.

Specification choicePostage consequence
Размер конвертаDetermines letter vs large envelope from the start
Плотность бумагиAdds to the loaded weight
Тип закрыванияSome closures are non-machinable
ОкноCan create uneven thickness
Rigid insertsPush a flat into parcel pricing

The economics are worth running before a large campaign rather than after: a small per-piece postage difference multiplied across a mailing list usually dwarfs the difference in envelope unit price. For packing and material choices that affect both postage and protection, see our конверты для доставки руководстве.

Check before orderingПочему
Finished, loaded weightDrives the weight step
Finished thicknessDrives the shape class
Rigidity after packingDrives flat vs parcel
Postage per piece × quantityUsually the dominant cost

Распространённые ошибки

ОшибкаПоследствиеИсправить
Weighing the empty envelopeWrong class and weight stepWeigh it loaded
Measuring thickness flat, not loadedLetter becomes flat unexpectedlyMeasure the stuffed piece
Assuming weight is all that mattersShape decides firstCheck shape before weight
Ignoring rigidityParcel price for a flat-size pieceFlex-test the contents
Assuming the surcharge applies to flatsOver-estimating a large envelopeThe surcharge is letters-only
Using rates read months agoPrices are revised periodicallyConfirm current rates
Designing the envelope after pricing postageRework neededSpecify size, stock and closure together

Заключение

Envelope postage rates follow a fixed sequence: shape first, then thickness and rigidity, then weight. Using USPS as the worked example, a letter must stay within 11½ × 6⅛ inches and ¼ inch thick and 3.5 ounces, and exceeding any one of those moves it to large-envelope pricing; a rigid flat-size piece moves further, to parcel pricing.

As of 12 July 2026 the USPS retail base is $0.82 for a 1 oz letter, $0.29 for each additional ounce, and $1.69 for a 1 oz large envelope, with a $0.49 non-machinable surcharge on letters. Those figures will change — confirm them against the carrier's current published rates before relying on them for a mailing.

Measure the loaded piece, not the envelope; check the flex before you check the weight; and specify envelope size, stock and closure together so that postage is part of the design rather than a surprise at the counter. For choosing the envelope itself, start with our большие почтовые конверты руководстве.

Need envelopes specified with postage class in mind? Запросить расчёт and tell us the contents — we will advise on size, stock and closure for your mailing.