Envelope Sizes

Envelop sizes are divided into two groups: the US or standard and the ISO metric system. The latter is utilized in Europe and other countries around the world.

US Sizes: Commercial Envelopes

These are used for business, checks, invoices and writing stationery. The sizes are: 3 1/2" x 6" (6 ¼), 3 5/8" x 6 1/2" 6 ¾), 3 7/8" x 7 1/2" (7 ¾), 3 5/8" x 8 5/8" (8 5/8) and 3 7/8" x 8 7/8" (9). The larger ones are 4 1/8" x 9 1/2" (10), 4 1/2" x 10 3/8" (11), 4 3/4" x 11" (12) and 5" x 11 1/2" (14).

Announcement Envelopes

These envelop sizes are used for invitations, brochures and announcements. The sizes are 4 3/8" x 5 3/4" (A-2), 4 3/4" x 6 1/2" (A-6), 5 1/4" x 7 1/4" (A-7), 5 1/2" x 8 1/8" (A-8), 6" x 9 1/2" (A-10 ) and 3 7/8" x 8 7/8" (slim).

Booklet Envelopes

These types are used for sending folders and catalogs. The sizes are 4 3/4" x 6 1/2" (3), 5 1/2" x 8 1/2" (5), 5 3/4" x 8 7/8" (6), 6" x 9" (6 ½), 6 1/4" x 9 5/8" (7), 7 1/2" x 10 1/2" (7 ½) and 8 3/4" x 11 1/2" (9). Three other large sizes are available: 9" x 12" (9 ½), 9 1/2" x 12 5/8" (10) and 10" x 13" (13).

Catalog Envelop Sizes

The sizes are: 6" x 9" (1), 6 1/2" x 9 1/2" (1 ¾), 6 1/2" x 10" (2), 7" x 10" (3), 7 1/2" x 10 1/2" (6), 8" x 11" (7), 8 1/4" x 11 1/4" (8), 8 1/2" x 10 1/2" (9 ½), 8 3/4" x 11 1/4" (9 ¾), 9" x 12" (10 ½), 9 1/2" x 12 1/2" (12 1/2), 10" x 13" (13 ½), 11 1/4" x 14 1/4" (14 ¼) and 11 1/2" x 14 1/2" (14 ½).

Other Envelope Types

Other kinds of envelopes used in the US include the window envelopes, (for paying bills), baronial envelopes (similar to announcement envelopes) and double window envelopes (used for checks).

ISO Envelop Sizes

The names and their size in millimeters and inches are described below.

C3: 324 x 458 mm / 12 3/4 x 18 in (for A3 paper size); B4: 250 x 353 mm / 9 7/8 x 13 7/ 8 in; C4: 229 x 324 mm / 9 x 12 3/4 in (A4 content format); B5: 176 x 250 mm / 7 x 9 7/8 in.

Other sizes are the following: C5: 162 x 229 mm / 6 3/8 x 9 in; B6; 125 x 176 mm / 5 x 7 in; C6: 114 x 162 mm / 4 1/2 x 6 3/8 in; C6/C5: 114 x 229 mm / 4 1/2 x 9 in; C7/6: 81 x 162 mm / 3 1/4 x 6 3/8 in and C7: 81 x 114 mm / 3 1/4 x 4 ½ in.

These envelop sizes are not the only ones available. There are other types used, although not as much as these.