Window Envelope Design Standards: Sizes, Window Placement and Print Specs

What Is a Window Envelope?

A window envelope is an envelope with a transparent panel cut into the front, letting the address printed on the letter inside show through — no need to print the address on the envelope itself. It is the standard for invoices, statements, payroll and direct mail, where thousands of letters are stuffed and mailed automatically.

Custom window envelopes give businesses full control over the window size, position, and the envelope’s print design. The most common format is the single-window #10 window envelope; double-window versions are used for mailings that show both a return address and a delivery address.

Window Envelope Sizes: Standard Dimensions

Envelope Style	Dimensions (in)	Window Position (typical)
#10 single window	4⅛ × 9½	⅞ in from left, ¾ in from bottom
#10 double window	4⅛ × 9½	Return window upper-left, address window lower
#9 single window	3⅞ × 8⅞	Same proportional position as #10
6 × 9 single window	6 × 9	Left side, mid-height
9 × 12 single window	9 × 12	Left side, mid-height
Custom window	Any size	Per artwork

Manufacturer’s note: Window sizes commonly range from 1⅛ × 3 in to 1¼ × 4 in. Custom window sizes and positions are die-cut, so anything within the printable area is possible — but standard positions cost less and run faster.

Window Position Rules (Postal & Print)

The window must line up with the address block on the letter inside. Two standards govern position:

USPS automation requirements — the delivery address must sit within the address zone of the envelope; the window must not obstruct the barcode clear zone
Print registration — the window is die-cut after printing, so a consistent die position (±1 mm) is what guarantees the address shows through fully

Standard #10 Window Position (mm from bottom-left of envelope)

Edge	Distance
Window left edge → envelope left edge	26 mm (1 in)
Window bottom edge → envelope bottom edge	19 mm (¾ in)
Minimum window size	25 × 76 mm
Maximum window size	32 × 102 mm

Design Rules for Window Envelope Artwork

Address block position: the address on the insert must sit inside the window area with at least 3 mm clearance on all sides
Safe margin: keep all other graphics 6 mm from the window edge — die-cut tolerance can shave into artwork that touches it
Window film: standard window film is clear 30–40 micron PET; anti-static and opaque-window variants are available for sensitive mail
Flap direction: specify whether the flap is on the back (standard) — this affects which side the window appears from

Printing Options for Custom Window Envelopes

Option	Detail
Full-color CMYK front	Branding around the window, common for billing and marketing mail
Security tint interior	Hides document content around the window area
Two-sided printing	Print on both front and back flap
Foil stamping	Premium window envelopes for luxury mailings

Common Window Envelope Design Mistakes

Address block misaligned with the window — the most common error; always test-stuff a proof
Graphics touching the window edge, clipped by die-cut tolerance
Using a matte film when barcode scanning is required (glare can cause non-reads)
Forgetting the return address window on double-window designs

FAQ

What is the standard window envelope size?
The most common is the #10 window envelope at 4⅛ × 9½ in, with a single window positioned ⅞ in from the left and ¾ in from the bottom.

Can I get custom window envelopes with my logo?
Yes — custom window envelopes can be printed full color with your logo and branding around any window size or position.

What is a double window envelope?
A double window envelope has two transparent panels: one for the return address and one for the delivery address, used for automated statement mailings.

Do window envelopes cost more than plain envelopes?
The window die-cut and film add a small per-unit cost, but automated addressing eliminates label and printing costs — for high-volume mailings, window envelopes are usually cheaper overall.

Can the window be on the left or right?
Yes. Standard is left; right-position windows are available for markets like the UK where addresses are positioned differently. Request a quote with your layout and we’ll confirm the die.