Tarifas de franqueo de sobres: cuánto cuesta enviar una carta o un sobre grande

Introducción

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 guía de sobres grandes para correo 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.

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

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:

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

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.

The Thickness and Rigidity Trap

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

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.

The Weight Test and the Per-Ounce Step

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

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.

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.

Worked examples using those rates:

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.

Six Reasons Postage Jumps a Tier

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

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.

Self-Checking Before You Go to the Post Office

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

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.

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 conversión de tamaños de sobre guide handles the unit comparison.

International Mail

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

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.

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.

What This Means for Envelope Specification

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

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 sobres para envío .

Errores comunes

Conclusión

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 guía de sobres grandes para correo .

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