shipping icon business envelopes Free shipping

FREE Ground Shipping site-wide. No minimums. Excludes PR, HI, AK, AS, VI, WA.
* More info
0 Back to Shopping
Back to all Articles

Envelope Size Chart: All Standard US Sizes, Dimensions, and Uses (2026)

Last updated: October 23, 2026

Choosing the wrong envelope size costs you time on every mailing: mis-sized print settings, inserts that do not fit, and postage class errors all trace back to a simple reference gap. This envelope size chart covers every standard US commercial, coin, and large-format envelope with exact dimensions in inches, USPS postage class, what fits inside each size, and the correct Word and Google Docs settings for printing.

Quick Answer: What Envelope Size Do I Need?

The right envelope size depends on what you are mailing and whether you want the contents to fold or stay flat. The #10 (4-1/8 x 9-1/2 inches) handles most standard business letters. The 9x12 holds 8.5x11 sheets flat without folding. Coin envelopes handle small items under 5 inches.

 

  • Standard business letter (8.5x11 tri-folded): use a #10 envelope (4-1/8 x 9-1/2 in)
  • Letter flat, no fold: use a 9x12 envelope (9 x 12 in); letter half-folded: use a 6x9 envelope
  • Return envelope inside a #10: use a #9 envelope (3-7/8 x 8-7/8 in)
  • Coins, keys, checks, and small parts: use coin or check envelopes
  • USPS letter rate ($0.82) applies to #6 3/4 through #14; flat rate ($1.63) applies to 9x12 and larger
  • Word printing: use Custom Size for any envelope not in the built-in dropdown (#11, #12, 9x12, 10x13)
If You Need To Mail... Best Envelope Size USPS Class 2026 Postage (1 oz)
Standard letter, tri-folded #10 (4-1/8 x 9-1/2 in) Letter $0.82
Letter flat, no fold 9x12 (9 x 12 in) Flat $1.63
Letter half-folded 6x9 (6 x 9 in) Letter or Flat* $0.82*
Reply/return envelope in a #10 #9 (3-7/8 x 8-7/8 in) Letter $0.82
Business check with stub Check envelope (8-7/8 x 3-7/8 in) Letter $0.82
Coins, keys, small parts #1 Coin (2-1/4 x 3-1/2 in) Letter $0.82
Legal document flat 10x13 (10 x 13 in) Flat $1.63

*6x9 qualifies for letter rate when contents are flexible and under 0.25 inches thick. Rigid or heavy contents shift it to flat rate. Verify before bulk mailing. Rates effective July 12, 2026, per USPS Notice 123.

Table of Contents

Commercial Envelope Size Chart (#6 3/4 Through #14)

Commercial envelopes are the standard format for business correspondence in the US. All sizes from #6 3/4 through #14 qualify for USPS letter-rate postage when contents meet USPS weight and thickness rules. The table below gives exact dimensions, what fits inside, and the correct Word setting for each size.

Size Dimensions (inches) What Fits Inside Word Setting Custom Size (W x H) Feed Orientation USPS Class 2026 Postage (1 oz)
#6 3/4 3-5/8 x 6-1/2 8.5x11 folded in quarters, short notes, receipts Size 6 3/4 6.5 x 3.625 Short edge first, face up Letter $0.82
#9 3-7/8 x 8-7/8 Reply or remittance slip, fits inside a #10 unsealed Size 9 8.875 x 3.875 Short edge first, face up Letter $0.82
#10 4-1/8 x 9-1/2 8.5x11 tri-folded (standard business letter) Size 10 (4 1/8 x 9 1/2 in) 9.5 x 4.125 Short edge first, face up Letter $0.82
#11 4-1/2 x 10-3/8 Longer documents, multi-page tri-folds Custom Size 10.375 x 4.5 Short edge first, face up Letter $0.82
#12 4-3/4 x 11 Thick multi-sheet packets, bulky tri-folds Custom Size 11 x 4.75 Short edge first, face up Letter $0.82
#14 5 x 11-1/2 Legal 8.5x14 tri-folded Custom Size 11.5 x 5 Short edge first, face up Letter $0.82

Postage rates effective July 12, 2026, per USPS Notice 123. Letter rate applies when total weight is under 3.5 oz and thickness is under 0.25 inches.

Shop commercial envelopes: 10 envelopes, all regular envelopes

Coin Envelope Size Chart

Coin envelopes are small-format envelopes used for coins, keys, seeds, small jewelry, bolts, USB drives, and any item too small for a standard commercial envelope. Business Envelopes carries three sizes, available in white and brown kraft.

Size Dimensions (inches) Common Uses Closure USPS Class
#1 Coin 2-1/4 x 3-1/2 Coins, keys, small jewelry, seeds, parts Gum flap Letter (as enclosure)
#7 Coin 2-7/8 x 4-7/8 Larger coins, folded receipts, small electronics Gum flap or peel-and-seal Letter (as enclosure)
4-5/8 x 6-3/4 4-5/8 x 6-3/4 Larger small-item payloads, document storage Open-end peel-and-seal Letter

Coin envelopes are rarely mailed on their own. They are typically enclosed inside a larger commercial envelope for outbound mailing, or used for internal organization, storage, and distribution. The 4-5/8 x 6-3/4 format is large enough to mail independently at letter rate.

Shop all sizes: coin envelopes

Large Format Envelope Size Chart (6x9 Through 10x15)

Large format envelopes hold 8.5x11 sheets flat or with minimal folding. USPS classifies these as flats rather than letters, which means flat-rate postage applies. Flat-rate postage is higher than letter rate per piece but allows more content without folding.

Size Dimensions (inches) What Fits Inside Word Custom Size (W x H) Feed Orientation USPS Class 2026 Postage (1 oz)
6 x 9 6 x 9 8.5x11 half-folded, brochures, small catalogs 9 x 6 Short edge first, face up Letter or Flat* $0.82 / $1.63*
9 x 12 9 x 12 8.5x11 flat unfolded, reports, contracts, brochures 12 x 9 Short edge first, face up Flat $1.63
10 x 13 10 x 13 Legal 8.5x14 flat, thick packets, bound reports 13 x 10 Short edge first, face up Flat $1.63
10 x 15 10 x 15 Oversized documents, 11x14 sheets, large catalogs 15 x 10 Short edge first, face up Flat $1.63

*The 6x9 qualifies for letter rate only when contents are flexible and under 0.25 inches thick and under 3.5 oz. Rigid or thick contents require flat rate. Always verify before bulk mailing. Rates effective July 12, 2026.

Shop large format envelopes: 9x12 envelopes, all sizes

USPS Postage Class Rules by Envelope Size

USPS assigns postage class based on the physical dimensions and weight of the sealed piece, not just the envelope type. Applying the wrong postage class results in pieces returned or charged postage due at delivery. The rules below apply to all standard commercial envelopes as of 2026.

When does an envelope qualify for letter rate?

An envelope qualifies for USPS First-Class letter-rate postage ($0.82 for 1 oz as of July 12, 2026) when all of the following apply:

  • Minimum dimensions: 3.5 inches tall x 5 inches long
  • Maximum dimensions: 6.125 inches tall x 11.5 inches long
  • Maximum thickness: 0.25 inches
  • Maximum weight: 3.5 oz
  • Rectangular shape with uniform thickness
  • Flexible (not rigid): the piece must bend under light pressure
  • Length-to-height ratio between 1.30 and 2.50

Square envelopes and envelopes with a length-to-height ratio outside that range require a non-machinable surcharge on top of the letter rate.

When does an envelope require flat rate?

An envelope requires USPS flat-rate postage ($1.63 for 1 oz as of July 12, 2026) when it exceeds the letter-size limits above. This includes 9x12 envelopes, 10x13 envelopes, 10x15 envelopes, and any piece thicker than 0.25 inches regardless of its footprint dimensions.

Envelope Size USPS Classification 2026 Postage (1 oz) 2026 Postage (2 oz) Notes
#6 3/4, #9, #10, #11, #12, #14 First-Class Letter $0.82 $1.11 Standard letter rate, most efficient for single-sheet mailings
6x9 (flexible contents) First-Class Letter $0.82 $1.11 Only when contents are thin and flexible; verify before bulk runs
6x9 (rigid or thick contents) First-Class Flat $1.63 $1.92 Apply flat rate when piece does not flex under light pressure
9x12, 10x13, 10x15 First-Class Flat $1.63 $1.92 Always flat rate; letter-rate stamps will result in postage due

Source: USPS Notice 123, effective July 12, 2026. Always verify current rates at usps.com/business/postage-rates before production runs.

How to Set Envelope Size for Printing in Microsoft Word

Word handles envelope printing through its built-in Mailings tool. The process works the same across Microsoft 365, Word 2019, and Word 2021. Standard sizes (#9, #10, #6 3/4) have dedicated entries in the dropdown. All other sizes require the Custom Size option.

Setting a standard size in Word

  1. Open Word and click the Mailings tab.
  2. Click Envelopes in the Create group.
  3. In the Envelopes and Labels dialog, click Options.
  4. Under Envelope Size, select the correct size from the dropdown (for #10, select Size 10 (4 1/8 x 9 1/2 in)).
  5. Click the Printing Options tab to confirm the feed orientation.
  6. Click OK, type or paste the delivery address, and click Print.

Setting a custom size in Word (#11, #12, #14, 6x9, 9x12, 10x13, 10x15)

  1. Follow steps 1 through 3 above.
  2. In the Envelope Size dropdown, scroll to the bottom and select Custom Size.
  3. Enter dimensions: use the long dimension as Width and the short dimension as Height. For a 9x12 envelope: Width 12 inches, Height 9 inches.
  4. Click Printing Options and verify the feed orientation matches how you load the envelope.
  5. Print one test piece on plain paper before running the full batch.
Envelope Size Word Setting Custom Size (W x H in Word)
#6 3/4 Size 6 3/4 6.5 x 3.625
#9 Size 9 8.875 x 3.875
#10 Size 10 (4 1/8 x 9 1/2 in) 9.5 x 4.125
#11 Custom Size 10.375 x 4.5
#12 Custom Size 11 x 4.75
#14 Custom Size 11.5 x 5
6 x 9 Custom Size 9 x 6
9 x 12 Custom Size 12 x 9
10 x 13 Custom Size 13 x 10
10 x 15 Custom Size 15 x 10

For the full printing setup guide including laser, inkjet, and bulk printer settings, see how to print on envelopes.

How to Set Envelope Size for Printing in Google Docs

Google Docs does not include a native envelope printing tool. Setting a custom page size is the most reliable method.

  1. Go to File, then Page setup.
  2. Set the paper size to Custom.
  3. Enter the envelope dimensions: for a #10 envelope, set Width to 9.5 inches and Height to 4.125 inches. Set orientation to Landscape.
  4. Set all margins to 0.5 inches.
  5. Position the delivery address approximately 2.5 inches from the top and 4 inches from the left using a text box.
  6. Before printing, go to File, Print and confirm the paper size in the print dialog matches your custom dimensions. Many print drivers override the page settings, so check both.
Envelope Size Google Docs Width Google Docs Height Orientation
#9 8.875 in 3.875 in Landscape
#10 9.5 in 4.125 in Landscape
#11 10.375 in 4.5 in Landscape
#12 11 in 4.75 in Landscape
#14 11.5 in 5 in Landscape
6 x 9 9 in 6 in Landscape
9 x 12 12 in 9 in Landscape
10 x 13 13 in 10 in Landscape
10 x 15 15 in 10 in Landscape

Paper Weight Guide for Envelope Printing

Paper weight determines how reliably an envelope feeds through laser and inkjet printers. Envelopes that are too light for the printer feed path cause jams, misfeeds, and smeared toner. The table below shows which weights work for each printer type.

Paper Weight Inkjet Laser High-Volume Laser Notes
20 lb Works Sometimes Not recommended Too thin for laser feed paths; curl risk under fuser heat
24 lb Works Works Works Recommended for most office printing; consistent feed and toner adhesion
28 lb Works Works Best Premium stock; preferred for high-volume laser and custom-printed programs

All standard white wove envelope formats at Business Envelopes are available in 24 lb stock as standard. 28 lb stock is available on select open-end and booklet formats for high-volume printing programs. See the full range at regular envelopes.

Address Placement Guide by Envelope Size

Once the size is set correctly in Word or Google Docs, the delivery address must be positioned within the USPS OCR read zone. Position is measured from the top-left corner of the document in landscape orientation before the envelope is loaded into the printer.

Envelope Size Return Address Position Delivery Address: From Top Delivery Address: From Left
#9 0.25 in from top-left corner 1.5 in 3.5 in
#10 0.25 in from top-left corner 2.0 in 4.0 in
#11 0.25 in from top-left corner 2.0 in 4.5 in
#12 0.25 in from top-left corner 2.0 in 5.0 in
#14 0.25 in from top-left corner 2.2 in 5.0 in
6 x 9 0.5 in from top-left corner 2.5 in 3.0 in
9 x 12 0.5 in from top-left corner 4.0 in 3.5 in

Always test before printing a batch. Print one test envelope, then hold the printed test piece over a blank envelope to confirm all address elements fall within the correct zones. For window envelopes, insert the document and confirm the address shows through with at least 1/8 inch clearance on all four sides of the window opening.

Window Envelopes: Size and Printing Settings

Window envelopes use the same size settings as plain envelopes of the same format. A #10 window envelope uses the same Size 10 setting in Word as a plain #10 envelope. The printing approach differs from standard envelopes in two important ways.

  • Do not print the delivery address on the envelope face. The window shows the delivery address from the enclosed document. Printing it on the envelope face creates a duplicate that confuses USPS OCR equipment.
  • Never print over the window area. The poly-film window is laser-safe, but it should not receive toner. Position return address and logo elements above and to the left of the window zone.
  • Custom-printed window envelopes have the return address and logo pre-printed at the factory. No return address printing step is needed at your printer.

Browse all formats at window envelopes and custom printed envelopes.

Shop Envelopes by Size

Business Envelopes has supplied envelope stock to US businesses since 1997. Every size in the chart above is in stock, with blank stock shipping same or next business day. Custom-printed envelopes with your logo and return address are available across all commercial sizes with no minimum order and a PDF proof before production.

  • No minimums on any order
  • Free ground shipping to the contiguous 48 states
  • Blank stock ships same or next business day
  • Custom-printed orders ship within 7 to 10 business days from proof approval

Browse all sizes: regular envelopes | #10 envelopes | 9x12 envelopes | coin envelopes | window envelopes | custom printed envelopes

Frequently Asked Questions

What size do I enter for a #10 envelope in Word?
In Word's Mailings tab, select Envelopes, then click Options. Under Envelope Size, select Size 10 (4 1/8 x 9 1/2 in). Load the envelope short-edge first (4.125-inch edge) with the address side face up in the manual feed tray. For other sizes, use Custom Size and enter the long dimension as width and the short dimension as height.
What is the difference between letter-rate and flat-rate envelope sizes?
Letter-rate sizes (#6 3/4, #9, #10, #11, #12, #14, and 6x9 on light contents) mail at $0.82 per ounce for First-Class mail in 2026. Flat-rate sizes (9x12, 10x13, 10x15) mail at $1.63 per ounce. USPS classifies any envelope over 6-1/8 inches tall or 11-1/2 inches long as a flat. Source: USPS Notice 123, effective July 12, 2026.
Which paper weight works best for printing on envelopes?
24 lb is the recommended paper weight for most office laser and inkjet printing. It feeds consistently, holds toner well, and does not curl under fuser heat. 20 lb works on most inkjet printers but can cause feed issues on laser printers. 28 lb is preferred for high-volume laser printing programs.
How do I set envelope size in Google Docs for printing?
Go to File, Page setup, Custom. For a #10 envelope, set width to 9.5 inches and height to 4.125 inches with landscape orientation. Set all margins to 0.5 inches. Position the delivery address approximately 2.5 inches from the top and 4 inches from the left. Always verify dimensions match in the print driver before printing the full batch.
Can I print on window envelopes?
Yes. Standard #10 window envelopes are laser-safe. Load them the same way as plain #10 envelopes , short edge first, address side face up. Do not print the delivery address on the envelope face. The window displays the delivery address from the document inside. See all formats at window envelopes.
What envelope size holds an 8.5 x 11 sheet without folding?
A 9x12 envelope holds a standard 8.5 x 11 sheet flat without folding. Enter 12 x 9 inches as the custom page size in Word or your print driver. This size mails at USPS flat rate ($1.63 per ounce in 2026).
What is the most common envelope size?
The #10 envelope (4-1/8 x 9-1/2 inches) is the most common business envelope size in the US. It holds a standard 8.5x11 sheet folded in thirds and is used for letters, invoices, billing statements, and general business correspondence. The #10 is also the size with the most variants, including window, double-window, and self-seal options.
What size envelope fits a standard letter?
A #10 envelope (4-1/8 x 9-1/2 inches) fits a standard 8.5x11 letter folded in thirds. A 9x12 envelope (9 x 12 inches) holds the same letter flat without folding. A 6x9 envelope holds the letter folded in half. The right choice depends on whether you want the letter to arrive folded or unfolded: 9x12 costs more in postage but preserves the document without crease marks.
What is the difference between a #9 and #10 envelope?
A #9 envelope measures 3-7/8 x 8-7/8 inches. A #10 envelope measures 4-1/8 x 9-1/2 inches. The #9 is designed to fit inside a #10 unsealed, which is why it is used as the standard return or reply envelope in outbound mailings. Billing statements, pledge campaigns, and direct mail programs routinely include a pre-addressed #9 inside a #10 outbound envelope for the recipient to use when responding.
How do I know what size envelope I need?
Measure the contents at their largest folded dimension. Add at least 1/4 inch to each measurement to allow comfortable insertion without jamming the flap. Match that measurement to the size chart: use a #10 for tri-folded 8.5x11 sheets, a 6x9 for half-folded sheets, a 9x12 for unfolded 8.5x11 sheets, and a coin envelope for items under 5 inches. When the contents are rigid, use a flat-rate envelope (9x12 or larger) regardless of the piece's overall dimensions.
What envelope sizes qualify for letter-rate postage?
Envelopes qualify for USPS First-Class letter-rate postage ($0.82 for 1 oz as of July 12, 2026) when they are between 3.5 x 5 and 6.125 x 11.5 inches, weigh under 3.5 oz, and are no thicker than 0.25 inches. This includes #6 3/4, #9, #10, #11, #12, and #14 envelopes. Envelopes over these limits, including 9x12 and 10x13, are classified as flats and require flat-rate postage at $1.63 for 1 oz.
What size envelope is used for checks?
The standard check envelope size is 8-7/8 x 3-7/8 inches, designed to hold a standard US business check (3.5 x 8.5 inches) with a check stub. Double-window check envelopes show both the payee address and the return address through pre-cut windows, eliminating the need to print on the envelope. Browse Business Envelopes' check envelopes for all available formats.
What are coin envelope sizes?
Coin envelopes are small envelopes for coins, keys, seeds, small jewelry, and small parts. Standard sizes include #1 Coin (2-1/4 x 3-1/2 inches) and #7 Coin (2-7/8 x 4-7/8 inches). A larger 4-5/8 x 6-3/4 format handles bigger small-item payloads. All sizes are available in white and brown kraft with gum flap or peel-and-seal closures. Shop all options at coin envelopes.
What is the custom size to enter in Word for a 9x12 envelope?
In Microsoft Word, select Custom Size in the Envelope Size dropdown under Mailings, Envelopes, Options. Enter Width: 12 inches and Height: 9 inches. Word treats the long dimension as width and the short dimension as height in landscape orientation. For a 10x13 envelope, enter Width: 13 inches, Height: 10 inches. For a 10x15 envelope, enter Width: 15 inches, Height: 10 inches.