11 Envelopes

The #11 envelope is the step up from the standard #10, and it earns its place in any office that regularly sends multi-page documents, checks alongside cover letters, or correspondence where a standard tri-fold in a #10 feels too tight. At Business Envelopes, we carry #11 envelopes in white gum flap, white window gum flap, and brown kraft gum flap, all available blank or with custom logo and return address printing. Free shipping on every order with no minimums.

#11 Envelope Size and Dimensions

The #11 envelope measures 4 1/2 inches tall by 10 3/8 inches wide (4.5 x 10.375 inches). It is a quarter inch taller and nearly a full inch wider than the standard #10, which measures 4 1/8 x 9 1/2 inches. That extra width is the functional difference between the two sizes. A standard 8.5 x 11 sheet folded into thirds fits in a #10 with roughly an eighth of an inch of clearance on each side. The same sheet in a #11 has significantly more room, which matters when you're inserting a folded document alongside a check, an additional enclosure, or a #9 return envelope plus a reply card.

Buyers searching "8 x 11 envelopes" or "8 1/2 x 11 envelopes" are typically looking for an envelope that accommodates standard letter-size paper. The #11 is the right commercial envelope format for that need when a #10 feels cramped. It mails at USPS First-Class letter postage when contents are under 3.5 oz, same as a #10, because the dimensions still fall within the letter-rate size window (maximum 6 1/8 x 11 1/2 inches). The #11 at 4 1/2 x 10 3/8 inches clears both dimensions cleanly.

When to Use a #11 Envelope Instead of a #10

The #10 is the default. The #11 is the right choice in specific situations where the #10 creates friction in the mailing process. Those situations include:

• Mailing a folded letter alongside a business check, where both need to fit without compressing
• Including a #9 or #6 3/4 return envelope plus a reply card inside the outgoing piece
• Sending a multi-page legal or financial document where the folded stack pushes against the #10 walls
• Running machine insertion where a tighter fit in a #10 causes jams or misfeeds
• Sending to clients where a slightly wider envelope conveys a more substantial outgoing piece

In each of these situations, the #11's extra quarter inch of height and additional width solves the operational problem cleanly. The postage cost doesn't change because the size still falls within letter-rate dimensions. You're not upgrading to a flat-mail format the way you would by moving to a 9 x 12.

Size 11 Envelopes: All Styles We Carry

#11 White Envelopes, Gum Flap

Plain bright white 24 lb wove stock with a moistenable gum flap. The standard format for everyday correspondence that needs a little more room than a #10 provides. Laser and inkjet compatible. Available blank or with custom logo and return address printing directly on the stock.

#11 Window Envelopes, Gum Flap

Clear poly-film window in the standard left-side position. Aligns with address blocks on standard letter templates and billing software when the document is folded into thirds, same as a #10 window envelope. Recipient address shows through from the document inside without any label or addressing on the envelope face. Used by legal offices, financial services firms, and accounting practices that mail document sets with checks or multi-page attachments too thick for a #10.

#11 Brown Kraft Envelopes, Gum Flap

Brown kraft stock in the #11 format. The kraft color signals a heavier-duty outgoing piece and is a natural fit for business-to-business correspondence where the brown envelope is already the house standard. Same dimensions as the white version: 4 1/2 x 10 3/8 inches. Available blank or with custom printing.

Custom Printing on #11 Envelopes

All three styles support custom printing. Return address, company name, logo, and tagline printed directly on the envelope stock before it ships. Not a label applied over blank stock. Direct printing holds through postal handling, doesn't peel at the edges, and arrives looking the same as it left. A PDF proof is sent before production begins, and artwork stays on file for reorders. Blank stock ships same or next business day. Custom printed orders ship in 7 to 10 business days from proof approval.

For offices running #11 envelopes as part of a broader mailing program that includes #10s and #9 return envelopes, the custom printing on all three sizes can carry the same return address and logo in the same position, producing a consistent visual identity across every piece in the outgoing and return envelope set. For volume pricing across multiple sizes and formats, request a bulk quote here. For the complete commercial envelope range including all sizes from #6 3/4 through #14, browse the full size catalog. If you need a window envelope in a larger format, the window envelope category covers #9, #10, #11, #12, and #14 sizes across all closure types.

Frequently Asked Questions About #11 Envelopes