There are many envelopes sizes available from most manufacturers and it is important to understand the different sizes available and what their uses are. Envelopes come in a range of sizes from smaller coin size envelopes up to larger 10×13 envelopes used for bigger items such as catalogs. There are envelopes for announcements, square envelopes and specialty envelopes with extra large flaps. There are also different flap designs. Square flaps, baronial, bankers, pointed, scalloped, standard commercial, etc. Most envelopes will have options and features available, including inside security tint, window(s), color paper, peel n seal closure and more. Today I am going to just explain the most common size business envelopes with a standard commercial flap which will narrow it down to just three sizes. I will start with the most common size envelope, the #10 Commercial Flap.
Measurement: 4-1/8 x 9-1/2
This envelope is most commonly used to send a tri-folded 8-1/2×11 standard letter size document. This could be a business letter, flyer, contract, advertising, billing, correspondence or even to send small marketing pieces like refrigerator magnets. The #10 envelope is also used as a business stationary envelope printed with company logo and address.
Measurement: 3-7/8 x 8-7/8
A little smaller than the #10 and that is by design. These are made to fit inside a #10 envelope. The #9 envelope can also fit an 8-1/2×11 sheet of paper (tri-folded) but just a bit snugger. Most commonly used as a business reply envelope and included in a mailing so the recipient can return send items back to a remit address usually pre-printed on the envelope. Sometimes there is a postage paid indicia on them or even a first class stamp. You would include a #9 envelope with an invoice or a statement to make it easier for a customer to pay the bill. The #9 envelope is also used to send checks. When ordered with a window, the check address will show through and since it is smaller than the #10 it fits snug for less movement inside the envelope assuring that the address can be read by the post office.
Measurement: 3-5/8 x 6-1/2
The smaller version of the #9 envelope. These are usually used for remittance envelopes to households. Because of the smaller size, made to fit personal checks. Popular with pool services, gardeners, newspapers and other direct to consumer businesses. The 6-3/4 envelope is also widely used for donations or fundraising by non-profit organizations. Also used by churches as church offering envelopes as an alternative to the higher cost of a specialized church offering envelope.