Introduction to Mailing Requirements

Proper understanding of Post Office regulations is a critical part. By following the guidelines and presorting the mail in-house, we are able to ensure that your mailing will pass postal regulations and will be sent in the most efficient manner possible.

Mail must adhere to the following regulations:

The mailing panel must have adequate room for a barcode
There cannot be extraneous information interfering with optical scanning in restricted areas including type, graphics or color backgrounds
The mailing indicia and all endorsements must be properly worded
It must be the appropriate size and quantity.

Letter Mail Requirements

Letter Specifications At-a-Glance
	A Max Height: 6.125 inches
	D Max Length: 11.5 inches
	B Min Height: 3.25 inches
	C Min Length: 5 inches
	Max Weight: 3.3 ounces
	Max Thickness: 0.25 inch
	Min Thickness: 0.007 inch
	Aspect Ratio: between 1.3 & 2.5

Standards for Machinable Letters
Machinable letter-size mail must be:

Not less than 5 inches long, 3-1/2 inches high, and 0.007-inch thick.
1. 0.007 inch thick if no more than 4-1/4 inches high and 6 inches long; or
2. 0.009 inch thick if more than 4-1/4 inches high or 6 inches long, or both.
Not more than 11-1/2 inches long, or more than 6-1/8 inches high, or greater than 1/4-inch thick.
Rectangular, with four square corners and parallel opposite sides. Letter-size, card-type mailpieces made of cardstock may have finished corners that do not exceed a radius of 0.125 inch (1/8 inch).

Weight Standards for Machinable Letters
The maximum weight for Presorted First-Class Mail machinable letters is 3.3 ounces (0.2063 pound). The maximum weight for Standard Mail machinable letters is 3.3 ounces (0.2063 pound).

Standards for Nonmachinable Letters
A letter-size piece is nonmachinable if:

It has an exterior surface that is not made of paper.
1. Windows in envelopes made of paper do not make mailpieces nonmachinable.
Attachments do not render mailpieces nonmachinable if allowed by eligibility standards according to the class of mail.
A letter-size piece is nonmachinable if it weighs more than 3.3 ounces, unless it has a barcode, weighs no more than 3.5 ounces, and is eligible for and claims automation letter prices or Standard Mail Carrier Route (barcoded) letter prices.
All letter-size pieces over 3.5 ounces are prepared as letters and charged the flat-size prices.

Maximum Corner Radius for Letter-Size Mailpieces
Corner Radius Maximum 1/8 inch

Maximum Weight, Machinable and Automation Letters
The following maximum weight limits apply:

Critical Mail letters: 3 ounces.
Machinable enveloped letters and cards: 3.3 ounces.
Automation enveloped letters and cards: 3.5 ounces

Rigid and Odd-Shaped Items
Rigid items (e.g., pens, pencils, keys, bottle caps) are prohibited within mailpieces. Reasonably flexible items (e.g., credit cards) are permitted. Odd-shaped items (e.g., coins and tokens) are permitted if firmly affixed to and wrapped within the contents of the mailpiece and envelope to streamline the shape of the mailpiece for automated processing. Die-cut flaps, those with irregular shapes, must be well sealed to the non-address side panel using tabs, glue spots or elongated glue lines; however, a 1/8 inch continuous glue line that follows and seals the contour of the shape is highly recommended.

Additional Letter Standards
Aspect Ratio
The aspect ratio (length of the mailpiece divided by height) must be between 1.3 and 2.5.

Wraps and Closures
An automation-compatible mailpiece may not be polywrapped, polybagged, or shrinkwrapped; have clasps, strings, buttons, or similar closure devices; or have protrusions that might impede or damage the mail or mail processing equipment.

Staples and Saddle Stitching
Staples or saddle stitching may be used only on booklet-type mailpieces to join the bound edge (spine). Inserted staples or stitching must parallel the bound edge, seat tightly and securely, and have no protrusions that might impede or damage the mail or mail processing equipment.

Flexibility Standards for Automation Letters
To ensure transport through automated mail processing machines, a mailpiece and its contents must bend easily when subjected to a transport belt tension of 40 pounds around an 11-inch-diameter drum.

USPS Services for Flexibility Testing
A mailer requesting flexibility testing for letter-size mailpieces must submit at least 5 mailpieces and a written request to their local postmaster or business mail entry manager for submission to the Pricing and Classification Service Center (PCSC) at least 6 weeks before the mailing date. The request must describe mailpiece contents and construction, number of pieces being produced, and preparation level. The PCSC will evaluate the piece and, if warranted, will instruct the mailer to submit samples to USPS Engineering for testing. The PCSC advises the mailer of its findings. If the mailpiece is approved, the letter includes a unique number identifying the piece and serves as evidence that the piece meets the relevant standards. A copy of the letter must accompany each postage statement submitted for mailings of the approved piece. If requested by the USPS, the mailer must show that pieces presented for mailing are the same as those approved.

Letter-Size Piece with Attached Release Card
A letter-size mailpiece, with one or two attached release cards, must have the following characteristics:

Be between 8 and 9-1/2 inches long (inclusive). With one release card affixed, be between 4 and 6 inches high (inclusive); with two release cards affixed, be between 5-1/2 and 6 inches high (inclusive).
No address element, including any address block barcode, may be closer than 1 inch to the right edge of the mailpiece.
Enveloped letters must be made of paper with a minimum 60-pound book grade paper and have a maximum thickness of 1/8 (0.125) inch. Window envelopes must have only one closed panel address window, no larger than 1-1/2 x 4-1/4 inches.
Card-type letters, not mailed at card prices, have a maximum thickness of 0.025 inch as mailed.
All letter-size pieces, other than enveloped letters and card-type pieces (such as folded self-mailers and booklets), must have a maximum thickness of 0.10 inch as mailed. Mailpieces with two affixed release cards must meet the following additional conditions:
1. Pieces requiring tabs must be sealed with 1-1/2 inch nonperforated tabs, unless larger tabs are required by standards for the specific mailpiece design.
2. Booklets must have a minimum cover weight of 70-pound book-grade paper.
3. Folded self-mailers must have a minimum cover weight of 100-pound book-grade paper.
Content insert shift must be no more than 5/8 inch horizontally and no more than 1/4 inch vertically.

Postcard Requirements

Postcard Specifications At-A-Glance
	A Max Height: 4.25 inches
	D Max Length: 6 inches
	B Min Height: 3.5 inches
	C Min Length: 5 inches
	Max Weight: 3 ounces
	Max Thickness: 0.016 inch
	Min Thickness: 0.007 inch
	Aspect Ratio: between 1.3 & 2.5

Dimensional Standards for Postcards

Not less than 3-1/2 inches high, 5 inches long, and 0.007 inch thick.
Not more than 4-1/4 inches high, or more than 6 inches long, or greater than 0.016 inch thick.
Rectangular, with four square corners and parallel opposite sides. Card-size pieces may have finished corners that do not exceed a radius of 0.125 inch (1/8 inch).

Maximum Corner Radius for Card-Type Mailpieces
Corner Radius Maximum 1/8”

Additional Postcard Standards
Address Side of Postcards
The address side of a card is the side bearing the delivery address and postage. The address side may be formatted to contain a message area. Presorted or automation card prices that contain a message area on the address side must be divided vertically or horizontally and meet the following additional standards, as applicable:

Vertically divided cards.

The address side of the card must be divided into a right portion and a left portion, with or without a vertical rule. The left portion is the message area.
The delivery address, postage, and any USPS marking or endorsement must appear in the right portion. The right portion must be at least 2-1/8 inches wide (measured from the right edge of the card, top to bottom inclusive).
For cards claimed at the Presorted price, nondelivery address information may extend into the right portion only above the address block and if the information is shaded or surrounded by a border that has at least 1/8 inch clearance between the delivery address block and the border. Mailers may choose not to shade or border the nondelivery address information if there is at least 1/8 inch of clear space around the delivery address block.

Horizontally divided cards.

The address side of the card must be divided into an upper and a lower portion, with or without a horizontal rule. The portion of the address side that does not contain the delivery address is the message area.
The delivery address, postage, and any USPS marking or endorsement must appear within the portion containing the delivery address. As an alternative, when the delivery address appears within the lower portion, it is permissible for the postage, return address, and any USPS marking or endorsement to appear in the upper portion. The portion bearing the delivery address must be at least 1-1/2 inches high (measured from the top or bottom edge of the card, as applicable, right edge to left edge inclusive).
For cards claimed at the Presorted price, nondelivery address information may extend into the portion containing the delivery address only if it appears above the address block and if the information is shaded or surrounded by a border that has at least 1/8 inch clearance between the delivery address block and the border. Mailers may choose not to shade or border the nondelivery address information if there is at least 1/8 inch of clear space around the delivery address block.

Double Postcards
A double card (a double stamped card or double postcard) consists of two attached cards, one of which is designed to be detached by the recipient and returned by mail as a single card.
Double cards are subject to these standards:

The reply half of a double card must be used for reply only and may not be used to convey a message to the original addressee or to send statements of account. The reply half may be formatted for response purposes (e.g., contain blocks for completion by the addressee).
A double card must be folded before mailing and prepared so that the address on the reply half is on the inside when the double card is originally mailed. The address side of the reply half may be prepared as business reply mail, courtesy reply mail, meter reply mail, or as a merchandise return service label.
Plain stickers, seals, or a single wire stitch (staple) may be used to fasten the open edge at the top or bottom once the card is folded if affixed so that the inner surfaces of the cards can be readily examined. Fasteners must be affixed according to the applicable preparation requirements for the price claimed. Any sealing on the left and right sides of the cards, no matter the sealing process used, is not permitted.

Enclosures in Double Postcards
Enclosures in double postcards are prohibited at card prices.

Standards for Release Postcards
One or two release cards, each at least 0.007 inch thick and no more than 0.012 inch thick, attached to a letter-size mailpiece must:

Be rectangular, but allowed with finished corners having a radius of at least 1/8 inch up to 1/2 inch.
Be between 2 and 2-1/2 inches (inclusive) high, and between 3 and 3-1/2 inches (inclusive) long. Affix each card with either edge parallel to the length of the mailpiece. Affix two cards on the same side of the mailpiece under these conditions:

Stack cards vertically, one above the other on the same side (address or non-address side, or
Affix cards side-by-side across the mailpiece length on the non-address side only.

Be affixed no closer to the bottom edge of the mailpiece than 7/8 inch and no further away from the bottom edge than 1-1/2 inches, and must not interfere with readability of the address, barcode, or postage information. When affixing two cards, these additional conditions apply:

When affixing cards one above the other on the address side, maintain a space of at least 1/2 inch from the leading edge, the trailing edge and the top edge.
When affixing cards one above the other on the nonaddress side, the right edge of the cards must be placed between 5 and 6 inches from the leading edge of the mailpiece, but no closer than 1/2 inch from the trailing edge. Maintain a space of at least 1/2 inch from the top edge.
When affixing cards side by side on the non-address side, the right edge of the leftmost card must be placed at least 5 inches from the leading edge of the mailpiece, and the rightmost card must be placed at least 1/2 inch from the trailing edge of the mailpiece. Maintain a space of at least 1/2 inch from the top edge.

Be affixed by machine to ensure adequate adhesion. Manually affixed attachments are not allowed.

Paper Weight Postcard
Postcards must be prepared from paper stock meeting the industry standard for a basis weight of 75 pounds or greater, with none less than 71.25 pounds.

Maximum Weight, Machinable and Automation Postcards
The following maximum weight limits apply:

Critical Mail letters: 3 ounces.
Machinable enveloped letters and cards: 3.3 ounces.
Automation enveloped letters and cards: 3.5 ounces

Aspect Ratio
The aspect ratio (length of the mailpiece divided by height) must be between 1.3 and 2.5.

Wraps and Closures
n automation-compatible mailpiece may not be polywrapped, polybagged, or shrinkwrapped; have clasps, strings, buttons, or similar closure devices; or have protrusions that might impede or damage the mail or mail processing equipment.

Self-Mailer Requirements

Self-Mailer Specifications At-A-Glance
	A Max Height: 6 inches
	D Max Length: 10.5 inches
	B Min Height: 3.5 inches
	C Min Length: 5 inches
	Max Weight: 3 ounces
	Max Thickness: 0.25 inch
	Min Thickness: 0.007 inch
	Aspect Ratio: between 1.3 & 2.5
	Max Panels: 12

Folded Self-Mailers Definition
A folded self-mailer is formed of two or more panels that are created when one or more unbound sheets of paper are folded together and sealed to make a letter-size mailpiece. The number of panels is determined by the number of sheets in the mailpiece and the number of times the sheets are folded.

Examples of Self-Mailers
Size, weight and closure requirements for different types of Self-Mailers. [ Examples ]

Physical Characteristics
Folded self-mailers have the following characteristics:

Height: A minimum of 3-1/2 inches and a maximum of 6 inches.
Length: A minimum of 5 inches and a maximum of 10-1/2 inches.
Thickness: A minimum of 0.007 inch; (0.009 inch if the height exceeds 4-1/4 inches or if the length exceeds 6 inches); the maximum thickness is 1/4 inch.
Maximum Weight: 3 ounces.
Rectangular, with four square corners and parallel opposite sides.
Aspect ratio: within 1.3 to 2.5.
Maximum number of panels: 12.
Quarter-folded self-mailers made of a minimum of 70-pound book grade paper may have as few as 4 panels. Quarter-folded self-mailers made of 55 pound or greater newsprint must have at least 8 panels and may contain up to 24 panels.

Additional Self-Mailer Standards
Panels
Panels are created when a sheet of paper is folded. Each two-sided section (front and back) created by the fold is considered one panel. When a folded self-mailer is made of multiple sheets, multiply the number of sheets by the number of panels created when folding a single sheet to determine the total number of panels. The following conditions apply:

External panels created by folding must be equal or nearly equal in size.
The final folded panel creates the back (non-address) side of the mailpiece. The open edge of the back panel must be at the top or within 1inch of the top or trailing edge of the mailpiece. For horizontal folded tri-fold or multi-fold pieces, the addressed panel may be the final folded panel if the leading edge is sealed.
The final folded edge must be the bottom of a folded self-mailer unless prepared as an oblong. The final folded edge of an oblong folded self-mailer must be the leading (right) edge.
Internal shorter panels must be covered by a full-size panel, and count toward the maximum number of panels. Optionally, internal shorter panels may be secured but must have only one edge that is shorter and be no further than one inch away from the edge of the external panel.
Folding methods and the subsequent number of panels created when folding a single sheet of paper are:

Bi-fold: folded once forming two panels.
Tri-fold: folded twice forming three panels.
Oblong: paper folded once to form two rectangular panels with one elongated dimension and parallel opposite sides. The final folded edge is on the leading (shorter) edge.
Quarter-fold: folded twice with each fold at a right angle (perpendicular) to the preceding fold. One sheet of paper quarter-folded creates four panels.

Flaps are formed when the final exterior panel is folded over and affixed to the unaddressed side of the mailpiece. Flaps must meet the following conditions:

The folded edge of a flap must be flush with the top edge of the mailpiece and end one inch or more above the bottom edge. Flaps must be at least 1-1/2 inches when measured from the top of the mailpiece.
Flaps must be secured by a sealing method.
Flaps with die-cut shapes must be firmly secured with tabs, glue line, glue spots or elongated glue lines. A 1/8 inch wide continuous glue line that seals the contour of the die-cut is strongly recommended.
Flaps on oblong pieces must be at least 5 inches long at the longest point when measured from the leading edge and must end more than one inch from the trailing edge.

Flaps and pockets prepared within folded self-mailers to stabilize enclosures are not considered to be panels.

Paper Weight and Sealing Requirements

Folded self-mailers:

Up to 1 ounce: 70 pound paper sealed with a continuous glue line, three glue spots; or elongated glue, or two 1-inch;
Over 1 ounce: 80 pound paper sealed with a continuous glue line, four glue spots; or four elongated glue lines; or two 1-1/2 inch tabs.

Quarter fold self-mailers:

Up to 1 ounce: 70 pound paper sealed with two 1-inch tabs.
Over 1 ounce: 80 pound paper sealed with two 1-1/2-inch tabs.

Optional design elements: Die-cut openings and perforated panes. Folded self-mailers with die-cut openings in the exterior panels must meet the following:

Up to 1 ounce: 100 pound paper sealed with or two 1-1/2-inch.
Over 1 ounce: 120 pound paper sealed with glue; or two 2-inch tabs; or three 1-1/2-inch tabs.

Optional design elements: Loose enclosures or attachments. For folded self-mailers that have loose enclosures or attachments the following applies:

Up to 1 ounce: 80 pound paper sealed with glue or two 1- 1/2-inch tabs.
Over 1 ounce: 100 pound paper sealed with glue; or two 2-inch tabs; or three 1-1/2-inch tabs.

Open-Sleeve Style Letter-Size Mailpieces
Open-sleeve style letter-size mailpieces consists of two symmetrical horizontal panels sealed together along the top and bottom edges or as a bi-fold that has a non-addressed panel permanently sealed to an inner flap along the top edge. Open-sleeve style mailpieces must meet the following conditions:

Join panels using 1/8 (0.125) inch continuous glue lines.
If flaps are used, they must be a minimum of at least 1-1/2 inches wide created as inner flaps adhered at the leading and trailing edges to the panel from which the flap is formed.

Perforated Pull-Open Strips and Pop-Out Panes
Folded self-mailers may be prepared with strips called panes that are pulled open to reveal the contents. These design elements must be placed only on the unaddressed side of the mailpiece and may be rectangular, circular, or oval shaped. Perforations, a row of small holes punched in a sheet of paper so that a section can be torn easily, are used to create pull-open strips, pop-out, or pop-open panes subject to the following requirements:

Two parallel perforated lines must be spaced at least 1/2 inch apart creating a pull open strip. Position perforated strips parallel to the height of the mailpiece at least 5 inches from the leading edge and 2 inches from the trailing edge. Position perforated strips parallel to the length of the mailpiece at least 1 inch from the top. Perforations have a 1mm cut (max)/1mm tie (min) ratio.
Pop-out panes with perforations around the outer edges have a maximum size of 4 inches long by 4 inches high. The following conditions apply:

Place panes at least 1 inch from any edge.
Use 1mm cut (max)/1mm tie (min) ratio.
When using two panes, space them at least 1 inch apart.
Address elements may not appear in perforated openings.

Pop-open panes with perforations on three sides must meet the following conditions:

The outer edges of the pull-open panel are a maximum of 4 inches long by 4 inches high.
If prepared with multiple panes, they must be spaced at least 1 inch apart.
Panes must be placed at least 1 inch from all edges.
Perforation patterns have 1 mm cut (max)/1 mm tie (min) ratio.

Perforated panes may not be prepared on pieces with die-cuts or on any mailpiece made of newsprint.

Loose Enclosures
Folded self-mailers with loose enclosures must be securely sealed to ensure containment of the enclosed material and prevent excessive enclosure shift during processing. Loose enclosures must be made of paper and must meet the following conditions:

Must be contained securely within the mailpiece.
Must be inserted in an interior pocket or secured by any method that prevents excessive shift during normal handling. Pockets are not counted as panels.
Folded self-mailers with die-cut openings may contain enclosures only if the inserted material is larger than the die-cut opening.
Enclosed material does not exceed the maximum thickness of:

0.05 inch thick for mailpiece weights up to 1 ounce.
0.09 inch thick for mailpiece weights over 1 ounce.

One empty reply envelope may be inserted within the first fold (manufacturing fold) of a quarter-folded self-mailer and must be secured within a fold to prevent separation during normal handing.

Addressing
When folded self-mailers are prepared with uncoated paper, printing addresses in a center or left-justified position within the optical character reader (OCR) area is recommended.

Die-Cut Elements
Folded self-mailers may be produced with two types of die-cut elements in the exterior panels: address windows or die-cut reveal. Die-cut openings may not be used to create die-cut punched holes (openings in the same location on all layers and panels so that there is a hole through the entire mailpiece). Prepare die-cut elements as follows:

Die-cut address windows (used to convey address information) must meet standards for window envelopes and meet the following additional conditions:

The maximum window size is 4 inches long by 2 inches high.
When an address window appears on a mailpiece, no other die-cut openings may be made on the exterior panels.

Die-cut openings used to reveal the contents of the mailpiece must be:

Limited to two on only one external panel.
Either circular with a 2-inch maximum diameter or rectangular with a maximum of 2 inches long by 1-1/2 inches high with slightly rounded 1/4 inch radius corners.
Placed at least 1-1/2 inches from all edges of the mailpiece if on the addressed side.
Placed at least 5 inches from the leading edge and 1-1/2 inches from all other edges if on the non-addressed side.
Positioned at least 1-1/2 inches apart when two or more die-cut openings are used.

A single 1/2-inch semi-circular die-cut thumb notch may be placed on the trailing edge of the addressed or unaddressed outer panel.

Booklet Requirements

Booklet Specifications At-A-Glance
	A Max Height: 6 inches
	D Max Length: 10.5 inches
	B Min Height: 3.5 inches
	C Min Length: 5 inches
	Max Weight: 3 ounces
	Max Thickness: 0.25 inch
	Min Thickness: 0.009 inch
	Aspect Ratio: between 1.3 & 2.5

Physical Standards for Booklets
Booklets must be:

Height: not more than 6 inches or less than 3.5 inches high.
Length: not more than 10.5 inches or less than 5 inches long.
Thickness: not more than 0.25 inch or less than 0.009 inch thick.
Weight: not more than 3 ounces.
Aspect ratio: within 1.3 to 2.5.

Booklets Definition
Booklets must have a bound edge (spine.) Sheets that are fastened with at least two staples in the manufacturing fold (saddle stitched), perfect bound, pressed-glued, or joined together by another binding method that produces a spine where pages are attached together are considered booklets. Booklets are open on three sides before sealing, similar in design to a book. In general, booklets must be uniformly thick. Large bound booklets that are folded for mailing may qualify for automation and machinable prices if the final mailpiece remains nearly uniform in thickness and conforms to all other automation standards.

Additional Booklet Standards
Paper
Booklet covers generally must be made with a minimum paper basis weight of 60-pounds or equivalent. Minimum basis weights are higher for some designs.

General Booklet Design and Sealing
The position of the final fold and intermediate fold (or spine) for letter-sized booklets varies according to the specific design of the mailpiece. Open edges can be sealed with tabs, cellophane tape, glue lines, or glue spots. Except for the simple spine wallet-style design with a height of 4 inches and a maximum length of 8 inches; tabs used as seals on the leading edge of small booklets less than 5 inches high, may be placed closer to the top and bottom edges than shown in Exhibit 3.16.5 through Exhibit 3.16.8 and may overlap in some cases. See Exhibit 3.16.5 through Exhibit 3.16.8 for design and sealing standards by type of design.

Flat Requirements

Flats Specifications At-A-Glance
	A Max Height: 12 inches
	D Max Length: 15 inches
	B Min Height: 6.125 inches
	C Min Length: 11.5 inches
	Max Weight: 3 ounces
	Max Thickness: 0.75 inch
	Min Thickness: 0.25 inch

Maximum Corner Radius for Flat-Size Mailpieces
Corner Radius Maximum 1/8 inch

General Definition of Flat Size Mail
Flat-size mail must have the following characteristics:

Be more than 11-1/2 inches long, or more than 6-1/8 inches high, or more than 1/4 inch thick.
Be not more than 15 inches long or more than 12 inches high or more than 3/4 inch thick, except for:

Polywrapped flats, with selvage that extends beyond the contents, up to a maximum length of 15-3/4 inches. The enclosed contents must not be longer than 15 inches.

Be rectangular with four square corners or with finished corners that do not exceed a radius of 0.125 inch (1/8 inch) unless prepared as Customized Market Mail.

Additional Flat Standards
Length and Height of Flats
The length of a flat-size mailpiece is the longest dimension. The height is the dimension perpendicular to the length. When determining the maximum height or length of a flat, include any selvage of polywrap material that may enclose the piece. When determining the minimum height or length of a flat, do not include the selvage of any polywrap material that may enclose the piece.

Minimum Flexibility for Flat-Size Pieces
Flat-size pieces must be flexible. Boxes—with or without hinges, gaps, or breaks that allow the piece to bend—are not flats. Tight envelopes or wrappers that contain one or more boxes are not flats. Test flats as follows:

All flats:

Place the piece with the length parallel to the edge of a flat surface and extend the piece halfway off the surface.
Press down on the piece at a point 1 inch from the outer edge, in the center of the piece’s length, exerting steady pressure.
The piece is not flexible if it cannot bend at least 1 inch vertically without being damaged.
The piece is flexible if it can bend at least 1 inch vertically without being damaged and it does not contain a rigid insert. No further testing is necessary.
Test if it can bend at least 1 inch vertically without being damaged and it contains a rigid insert.

Uniform Thickness
Flat-size mailpieces must be uniformly thick so that any bumps, protrusions, or other irregularities do not cause more than 1/4-inch variance in thickness. When determining thickness, exclude the outside edges (1 inch from each edge) when the contents do not extend into those edges. Also, exclude the selvage of any polywrap covering from this determination. Mailers must secure nonpaper contents to prevent shifting of more than 2 inches within the mailpiece if shifting would cause the piece to be nonuniformly thick or result in the contents bursting out of the mailpiece.

Standards for Non-Automation Flats
First-Class Mail

First-Class Mail flats cannot exceed 13 ounces. First-Class Mail flats weighing more than 13 ounces are Priority Mail.
Flat-size pieces that do not meet the standards must be prepared as parcels and pay the applicable parcel price.

Standard Mail

Each piece must weigh less than 16 ounces.
Flat-size pieces that do not meet the standards must be prepared as parcels and pay the parcel prices.

Bound Printed Matter

Flat-size pieces that do not meet the standards must be prepared as parcels and pay the applicable parcel prices.
Bound Printed Matter may not weigh more than 15 pounds.
Two or more flats may be mailed as a single piece if they are about the same size or shape or if they are parts of one article, if they are securely wrapped or fastened together, and if they do not together exceed the weight or size limits.

Media Mail and Library Mail

Flat-size pieces that do not meet the standards must be prepared as parcels.
No piece may weigh more than 70 pounds.
Two or more flats may be mailed as a single piece if they are about the same size or shape or if they are parts of one article, if they are securely wrapped or fastened together, and if they do not together exceed the weight or size limits.

Standards for Automation Flats
Shape and Size
Each flat-size piece must be rectangular, except that flat-size mailpieces may have finished corners that do not exceed a radius of 0.125 inch (1/8 inch). The following minimum and maximum dimensions apply to First-Class Mail, Standard Mail, Periodicals and Bound Printed Matter pieces:

Minimum height is 5 inches. Maximum height is 12 inches.
Minimum length is 6 inches. Maximum length is 15 inches, except for polywrapped flats.
For bound or folded pieces, the edge perpendicular to the bound or folded edge may not exceed 12 inches.
Minimum thickness is 0.009 inch. Maximum thickness is 0.75 inch.

Maximum Weight
Maximum weight limits are as follows:

For Critical Mail, 13 ounces.
For First-Class Mail, 13 ounces.
For Periodicals, 20 ounces.
For Standard Mail, less than 16 ounces.
For Bound Printed Matter, 20 ounces.

Additional Automation Flat Standards

Prohibitions
Protrusions
Clasps, strings, buttons, or like materials, or other protrusions that impede or damage mail processing equipment are prohibited.

Staples
Staples must not be substituted for tabs or wafer seals on pieces in automation price mailings.

Tabs, Wafer Seals, Tape, and Glue
Although not required, mailpieces may be prepared with tabs, wafer seals, cellophane tape, or permanent glue (continuous or spot) if these sealing devices do not interfere with the recognition of the barcode, price marking, postage information, and delivery and return addresses. Cellophane tape may not be placed over the barcode or where any part of the barcode will be printed. Tabs or seals placed in the area on which any part of the barcode is printed must contain a paper face meeting the standards for background reflectance.

Short Covers
Flats may be prepared with a cover page or protective cover that is more than 3/4 inch from each edge if the cover page is secured with at least two tabs, wafer seals, or glue spots placed within 1 inch of the top and bottom edges of the cover page or protective cover.

Uniformity and Exterior Format
A flat-size mailpiece prepared and claimed at automation prices must be uniformly thick. Each flat-size mailpiece must have a smooth and regular shape and be free of creases, folds, tears, or other irregularities not compatible with automation equipment. The exterior surface must not have protuberances caused by prohibited closures; attachments (except as provided below); irregularly shaped or distributed contents; or untrimmed excess material from the envelope, wrapper, or sleeve.

Outside Attachment
An attachment to a flat-size mailpiece must be a single sheet, the same size as the cover. The attachment must be permanently, securely, and uniformly affixed to the front or back cover along a bound, folded, or otherwise closed edge. Pieces claimed at a Periodicals price may bear attachments only if permitted by the applicable standards.

Booklet-Type Piece or Magazine
The contents of flat-size mailpieces prepared in sleeves or other wrappers must be sufficiently secure in the sleeve or wrapper to stay in place during processing. If material bearing the delivery address or barcode for the mailpiece is enclosed in a partial wrapper, that wrapper must be sufficiently secure to prevent the contents from shifting and obscuring the delivery address or barcode.

Mailing Information Booklet Download

Some text..

Mailing Services — Mail Requirements

There are a host of rules to know for getting your mail accepted by the USPS and getting the best rates. We have tried to go over the basics in these tabs. If you can create your mailing pieces to these specifications, then there should be no problems mailing them.