USPS flat rate envelope: price, sizes and when it pays

The USPS flat rate envelope costs one price for any weight and any US address. Compare it with the price by weight for your own ZIP Codes.

Independent site, not the Postal Service: prices read in its own price files.

Where you mail it

Where it is delivered

Packed, box included. Up to 70 lb

0 to 15.9; 16 oz make 1 lb

Example: 1 lb from 10001 to 90012· change a figure to see yours

Priority Mail Flat Rate Envelope at the Post Office

$13.90

Envelope saves $4.05 against paying by weight

Same envelope, online label$11.97
Same envelope from Jan 17, 2027 (proposed)$14.04
Priority Mail by weight, zone 8$17.95
How this is computed

Compiled by Radif Partners · How the prices are built

A USPS flat rate envelope is a Postal Service envelope sold with Priority Mail or Priority Mail Express at one price, whatever it weighs up to 70 pounds and wherever it goes in the United States, provided its flap closes normally. Three models exist for each service: the regular envelope of 12 1/2 by 9 1/2 inches, the legal envelope of 15 by 9 1/2 inches and the padded envelope. At a Post Office counter today the Priority Mail Flat Rate Envelope costs $13.90, the legal one $14.25 and the padded one $15.00; online, the regular envelope costs $11.97. These prices include the holiday increase in force until January 16, 2027. The Express envelope, with its guaranteed date, costs $38.25. On January 17, 2027 the regular Priority Mail envelope would cost $14.04 with the proposed 11% fuel surcharge, against $12.90 in July 2026. Only envelopes made by the Postal Service and marked Flat Rate qualify.

USPS flat rate envelope prices by model

The table lists the six flat rate envelopes of the Notice 123 price list, with their size, the counter price today, the online price and the proposed price from January 17, 2027, fuel surcharge counted.

Notice 123: Priority Mail and Priority Mail Express flat rate envelopes.
EnvelopeSizePost OfficeOnlinefrom Jan 17, 2027
Priority Mail Flat Rate Envelope12 1/2 x 9 1/2 in$13.90$11.97$14.04
Priority Mail Legal Flat Rate Envelope15 x 9 1/2 in$14.25$12.51$14.37
Priority Mail Padded Flat Rate Envelope12 1/2 x 9 1/2 in$15.00$12.84$15.21
Priority Mail Express Flat Rate Envelope12 1/2 x 9 1/2 in$38.25$33.46$38.74
Priority Mail Express Legal Flat Rate Envelope15 x 9 1/2 in$38.55$33.78$39.07
Priority Mail Express Padded Flat Rate Envelope12 1/2 x 9 1/2 in$39.25$34.05$39.79

When the envelope beats the scale

The regular Priority Mail envelope wins from zone 5 for a 1-pound piece and from zone 3 for 2 pounds, at counter prices. Below those zones, the same piece in your own envelope costs less by weight. The calculator does the comparison for your two ZIP Codes.

Envelope or price by weight

Example: 1 lb from 10001 to 90012· change a figure to see yours

Priority Mail Flat Rate Envelope at the Post Office

$13.90

Envelope saves $4.05 against paying by weight

Same envelope, online label$11.97
Same envelope from Jan 17, 2027 (proposed)$14.04
Priority Mail by weight, zone 8$17.95
Back to the full calculator at the top →

Filling a flat rate envelope

The envelope must close with its own flap, without being stretched out of shape by its contents. A plain Priority Mail envelope without the Flat Rate marking is charged by weight and zone, like your own envelope. For bulkier things, the flat rate boxes start with the small box, and for a guaranteed date the Express envelope is on the overnight shipping page.

Questions people ask before they mail

Tap a question to see the answer.

How much does a USPS flat rate envelope cost?

At a Post Office counter today: $13.90 for the Priority Mail Flat Rate Envelope, $14.25 for the legal size and $15.00 for the padded one. A label bought online costs less, $11.97 for the regular envelope. Priority Mail Express envelopes cost more because they come with a delivery date guarantee.

Is the padded flat rate envelope worth the extra cost?

The padded envelope costs $1.10 more than the regular one at the counter. It protects small items such as a phone case or jewelry without a box. For flat papers, the regular or the legal envelope is enough, and the legal size takes long documents without folding them.

When is paying by weight cheaper than the envelope?

For a light piece going a short distance. A 1-pound Priority Mail package in zone 1 costs $11.50, less than the $13.90 envelope, while 2 pounds across the country cost $22.55. For papers under 8 ounces with no hurry, Ground Advantage costs $10.20 even in zone 8.

Next steps

Flat rate box prices

Envelope, small, medium and large box: today, online and in 2027, and when each one wins.

Priority Mail rates

Two to three days, priced by the pound and zone, at the counter and online.

USPS overnight shipping cost

The fastest USPS service: price by weight and distance, the envelope and the Sunday fee.

Cheapest way to ship

The USPS options ranked by price for your package: Media Mail, Ground Advantage online, flat rate.

Postal Service price files, manual chapters and filings behind this page (4)

Each price, rule and zone was read in these documents on November 13, 2026.

Compiled by

Independent publisher of US parcel price tables built from the Postal Service's Notice 123 price files and its domestic zone chart. Paid by no carrier: no commission, no affiliate link, no paid placement.

Checked on · Editorial policy · Contact

Prices are read from the Postal Service price files, never estimated. They leave out pickup, special handling, hazardous material and any extra service you add at the counter. The January 17, 2027 prices are proposed and await review by the Postal Regulatory Commission.