12 Envelopes

The #12 envelope is the step up from the standard #10 for correspondence that needs more room without moving to a flat-document format. At 4 3/4 inches tall by 11 inches wide, it accommodates a standard letter folded into thirds with extra clearance, a check alongside a multi-page statement, or documents that fit awkwardly in a #10 but don't warrant a full 9 x 12 catalog mailer. At Business Envelopes, we carry #12 envelopes in plain white and white window configurations, both with moistenable gum flap closure, available blank or with custom logo and return address printing. Free shipping on every order with no minimums.

What Is the #12 Envelope Size?

A #12 envelope measures 4 3/4 inches tall by 11 inches wide (4.75 x 11 inches). It is larger than a standard #10 on both dimensions: three quarters of an inch taller and one and a half inches wider. That extra width is significant. A standard letter-size sheet folded into thirds produces a folded panel roughly 3.67 x 8.5 inches. In a #10, the fit is close with an eighth of an inch of clearance on each side. In a #12, the same folded panel has substantially more room, which means it loads more easily, doesn't bunch at the corners under the envelope walls, and allows for a second enclosure alongside the letter without the envelope bulging visibly.

In metric, the #12 envelope measures approximately 121 x 279 mm. The "#12" designation, like all commercial envelope numbers, comes from the standardized classification system introduced in the 1870s and has no direct relationship to the physical dimensions. What matters operationally is the 4 3/4 x 11 inch footprint and how it fits into your mailing workflow.

#12 Envelope Size vs. #10 and #11: When to Use Each

Understanding where the #12 fits in the commercial envelope hierarchy makes the purchase decision straightforward.

The #10 envelope at 4 1/8 x 9 1/2 inches is the standard for everyday business letters, invoices, and statements with a single sheet of paper. It's the most common commercial envelope in the U.S. and handles the overwhelming majority of business correspondence. The #11 at 4 1/2 x 10 3/8 inches adds a quarter inch in each direction, fitting a folded letter with a bit more room and accommodating a check alongside a short letter without the envelope becoming overstuffed. The #12 at 4 3/4 x 11 inches takes another step in both dimensions and is the right choice when the #11 still feels tight or when the correspondence regularly includes multiple enclosures, a check plus a multi-page statement, a folded letter plus a reply card, or any combination that makes a #10 or #11 look visibly thick.

Legal offices, financial services firms, and insurance companies that send correspondence with multiple attachments keep #12 envelopes in stock as their standard for thicker outgoing mail. It avoids the overstuffed appearance of a #10 running close to its maximum capacity while keeping the mailing in the letter-rate format, since the #12 qualifies for USPS First-Class letter postage when contents are under 3.5 oz.

#12 Business Envelopes: Styles We Carry

#12 White Envelopes, Gum Flap

Plain bright white 24 lb wove stock with a moistenable gum flap. Clean and professional for all-purpose correspondence, legal filings, financial documents, and any mailing where the larger #12 format is the right fit. Available blank or with custom logo and return address printing directly on the envelope face.

#12 White Window Envelopes, Gum Flap

Same bright white wove stock with a clear poly-film address window. The window position aligns with standard document address blocks, so the recipient's address shows through from the document inside without any labeling or envelope addressing. For billing operations, insurance correspondence, and financial services mailings where the #12 size is needed and the window eliminates the addressing step on every outgoing piece. Available with custom return address and logo printing on the face.

No 12 Envelopes: What That Search Usually Means

Buyers searching "no 12 envelopes" are typically asking about the number 12 commercial envelope size. The "no" prefix is the abbreviated form of "number," used the same way as "no 10" refers to the #10 envelope. Both searches refer to the same 4 3/4 x 11 inch commercial envelope. This size sits between the widely stocked #11 and the larger #14 in the commercial hierarchy and is less commonly carried by general office supply retailers, which is why buyers often search for it specifically by number rather than by dimension.

Custom Printing on #12 Business Envelopes

Both #12 styles in this lineup support custom printing. Return address, company name, logo, tagline, and any standard brand treatment printed directly on the envelope stock, not on an adhesive label. The printing is positioned to the upper left of the envelope face with the document address block visible through the window on the window version. A PDF proof is provided before production begins, and nothing runs until you've approved the layout. Artwork stays on file for reorders.

For other commercial envelope sizes that serve adjacent needs in a mailing program, our #10 envelope range covers standard correspondence and our full window envelope catalog covers #9, #10, #11, #12, and #14 formats. For flat-document mailing at the 9 x 12 format that doesn't need to fold, browse the 9 x 12 envelope category. For high-volume custom print programs across multiple sizes, request a bulk quote here and we'll price the full program together.

Frequently Asked Questions About #12 Envelopes