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USPS prices mail by shape first and weight second. Postcards, letters, and flats (large envelopes) each have their own price table, so a piece’s size, thickness, and flexibility set its postage before it is weighed, and that shape is fixed once the piece is designed.
For statements and invoices, the cheapest shape is usually a folded letter: at First-Class automation prices it costs $0.621 to $0.707 up to 3.5 ounces, compared with $1.605 to $2.165 for the same 3-ounce statement mailed flat.
For marketing mail, choosing the shape, mail class, and presort level before design starts can cut postage by 77% or more. All prices are from the USPS price list effective July 12, 2026.
How does USPS classify mail by shape?
USPS divides mail that isn’t a parcel into three price shapes: postcards, letters, and flats (large envelopes). A piece’s length, height, thickness, and flexibility decide its shape under the USPS Domestic Mail Manual. Each shape has its own price table, and weight is priced within that table.
In First-Class Mail, postcards are the cheapest shape and flats are the most expensive. A piece that breaks its shape’s handling rules pays a surcharge or moves to a more expensive category.
Why does mail shape affect postage?
Mail shape affects postage because USPS prices each piece by the cost of the equipment that sorts it. Letters and postcards run on high-speed letter sorters built for small, thin, flexible rectangles. Flats need separate flat-sorting equipment.
Pieces that no machine can handle are sorted by hand, the most expensive option, so they pay a surcharge or parcel prices.
How big can a postcard be, and how much does it cost?
A retail First-Class postcard costs $0.65 and must be a rectangle from 3.5 x 5 inches up to 4.25 x 6 inches, 0.007 to 0.016 inch thick. It is the lowest retail price for any shape.
USPS retail postcard size limits (effective July 12, 2026)
| Dimension | Minimum (in) | Maximum (in) |
|---|---|---|
| Length | 5 | 6 |
| Height | 3.5 | 4.25 |
| Thickness | 0.007 | 0.016 |
- A retail card larger than 4.25 x 6 inches is priced as a letter, at $0.82.
- Card stock thinner than 0.007 inch is not mailable.
- Presorted (commercial) First-Class postcards can be up to 6 x 9 inches and cost $0.453 to $0.495 each. Cards larger than 4.25 x 6 inches must be at least 0.009 inch thick to get card prices.
- A 6 x 11 “jumbo postcard” is 2 inches longer than the 9-inch presort limit, so it mails at letter prices. In bulk, letter prices can still be low.
Confirm card size with your mail house before printing, since a misjudged card falls into letter pricing.
What counts as a letter, and how much does it cost?
A USPS letter is a rectangular piece 5 to 11.5 inches long, 3.5 to 6.125 inches high, 0.007 to 0.25 inch thick, and no heavier than 3.5 ounces. Standard #10 business envelopes, 6 x 9 envelopes, and greeting-card envelopes all qualify.
First-Class Mail letter prices (effective July 12, 2026)
| Weight (not over) | Stamped | Metered |
|---|---|---|
| 1 oz | $0.82 | $0.78 |
| 2 oz | $1.11 | $1.07 |
| 3 oz | $1.40 | $1.36 |
| 3.5 oz | $1.69 | $1.65 |
Each additional ounce adds $0.29, up to the 3.5-ounce limit. A letter over 3.5 ounces is priced as a flat: a 4-ounce piece costs $2.56, compared with $1.69 for a 3.5-ounce letter.
What is the USPS nonmachinable surcharge?
The USPS nonmachinable surcharge is $0.49 per piece, charged on letters that can’t run through sorting equipment. It raises a 1-ounce stamped letter from $0.82 to $1.31, a 60% increase. The Domestic Mail Manual lists these triggers:
- Square or odd proportions. A letter’s length divided by its height must fall between 1.3 and 2.5. A square envelope has a ratio of 1, so it fails.
- Rigid pieces that won’t bend, such as envelopes stiffened with cardboard.
- Clasps, strings, buttons, or similar closures.
- Lumpy contents such as keys, pens, coins, or USB drives that make thickness uneven.
- Plastic wrapping or a non-paper exterior, such as a polybag. Paper envelopes with windows are fine.
- Address parallel to the short side, as on a vertical-format design.
What counts as a flat (large envelope), and how much does it cost?
A USPS flat is any piece that exceeds one letter maximum (longer than 11.5 inches, taller than 6.125 inches, or thicker than 0.25 inch), up to 15 x 12 inches, 0.75 inch thick, and 13 ounces. A 1-ounce flat costs $1.69. Catalogs, magazines, and documents mailed unfolded in 9 x 12 or 10 x 13 envelopes are typical flats; flats over 13 ounces must go Priority Mail.
First-Class Mail flat retail prices (effective July 12, 2026)
| Weight (not over) | Retail price |
|---|---|
| 1 oz | $1.69 |
| 2 oz | $1.98 |
| 3 oz | $2.27 |
| 4 oz | $2.56 |
| 8 oz | $3.72 |
| 13 oz | $5.24 |
Flat prices are higher than letter prices at every weight: a 1-ounce flat costs the same as a 3.5-ounce letter. If the contents can be folded to fit a letter envelope, mailing them as a letter costs less.
To get flat prices, a large envelope must also be flexible, rectangular, and uniformly thick. A rigid, nonrectangular, or lumpy large envelope is priced as a parcel. At retail that means USPS Ground Advantage, which starts at $7.90 on the standard price list and at $8.40 under the temporary holiday prices that run from October 4, 2026, until January 17, 2027.
Letter vs. flat vs. postcard: 2026 USPS price comparison
At every price level, a USPS letter costs roughly half as much as a flat, and in First-Class Mail a postcard costs less than either. The table compares 1-ounce prices by shape under the July 12, 2026 price list.
USPS 1-ounce prices by shape and service (effective July 12, 2026)
| Shape | Size limits (L x H x T) | Max weight | Retail stamped | Metered | First-Class presort (Mixed to 5-Digit) | Marketing Mail presort (Mixed to 5-Digit) |
|---|---|---|---|---|---|---|
| Postcard | 5–6 x 3.5–4.25 x 0.007–0.016 in (retail) | — | $0.65 | $0.65 | $0.495–$0.453 | Mails as a letter |
| Letter | 5–11.5 x 3.5–6.125 x 0.007–0.25 in | 3.5 oz | $0.82 | $0.78 | $0.707–$0.621 | $0.467–$0.395 |
| Nonmachinable letter | Letter size with a nonmachinable trait | 3.5 oz | $1.31 | $1.27 | $1.128–$0.844 | $1.299–$0.886 |
| Flat | Up to 15 x 12 x 0.75 in | 13 oz | $1.69 | $1.69 | $1.585–$1.025 | $1.260–$0.783 |
| Rigid or lumpy “flat” | Fails flat flexibility rules | — | Parcel price, from $7.90 ($8.40 until Jan. 17, 2027) | — | — | — |
Mixed is the least-sorted tier and 5-Digit the most sorted. Presort and Marketing Mail prices assume Intelligent Mail barcodes and the required minimum volumes; Marketing Mail flat prices apply to pieces up to 4 ounces. Nonmachinable rows show nonautomation presort prices. Source: USPS Notice 123.
Which mail design choices raise postage?
Seven common design choices add a surcharge, move a piece into a more expensive shape, or make it unmailable:
- Square envelopes. A letter-size square envelope pays the $0.49 nonmachinable surcharge on every piece.
- Mailing a few pages flat. Three sheets in a 9 x 12 envelope cost $1.69; tri-folded into a #10 envelope, they cost $0.82.
- Overstuffing a letter. Past 3.5 ounces or 0.25 inch thick, a letter becomes a flat: $1.69 at 3.5 ounces becomes $2.56 at 4 ounces.
- Treating a jumbo card as a postcard. A 6 x 11 card pays letter prices, not the $0.65 postcard price.
- Adding dimensional inserts. A pen, magnet, key card, or clasp can make a letter nonmachinable, or turn a flat into a parcel at $7.90 or more.
- Vertical layouts. An address that runs along the short side makes a letter nonmachinable.
- Ultra-thin card stock. Stock under 0.007 inch is not mailable, and pieces larger than 4.25 x 6 inches that are thinner than 0.009 inch pay the nonmachinable surcharge. Check paper caliper before ordering.
To catch these before the full print run, weigh and measure a fully assembled sample, inserts included, or send Tab Service a sample to review.
How much can bulk mail save by shape and presort level?
In a bulk mailing, shape, mail class (First-Class or Marketing Mail), and presort level together set the price per piece, and changing all three can cut postage by more than 80%.
Postage for 10,000 one-ounce pieces (USPS prices effective July 12, 2026)
| Format and service | Price per piece | Postage for 10,000 pieces |
|---|---|---|
| Flat, retail stamps | $1.69 | $16,900 |
| Flat, First-Class automation (Mixed) | $1.585 | $15,850 |
| Flat, Marketing Mail automation (5-Digit) | $0.783 | $7,830 |
| Letter, Marketing Mail automation (5-Digit) | $0.395 | $3,950 |
| Letter, Marketing Mail Saturation (EDDM-eligible) | $0.255 | $2,550 |
Switching from retail flats to 5-Digit Marketing Mail letters saves $12,950 per 10,000 pieces, or 77%. Saturation letters save $14,350, or 85%; Saturation requires mailing to at least 90% of residential addresses or 75% of all addresses on each carrier route. Because the design fixes the shape, choose shape and mail class before design starts.
Commercial prices come with requirements:
- A USPS annual mailing fee of $390 per mail class at each post office where you mail, plus a one-time $390 permit imprint application if you print an indicia instead of using stamps or a meter.
- Intelligent Mail barcodes and address quality standards.
- Minimum volumes: 200 pieces or 50 pounds for Marketing Mail, and 500 pieces for First-Class automation.
- Bills and statements of account must go First-Class Mail. Marketing Mail prices apply only to mail not required to go First-Class, such as advertising.
- Authorized nonprofits pay lower Marketing Mail prices; see our guide to nonprofit Marketing Mail eligibility.
A mail service provider handles these requirements and sorts each job to the deepest presort tier it qualifies for.
Let Tab Service find your lowest-cost mail format
Tab Service Company prints and mails direct mail marketing and transactional mail such as statements and invoices. We review your piece’s size, weight, and mail class, flag anything that could trigger a surcharge, and recommend the lowest-cost format. Contact Tab Service before your next campaign goes to print.
