The #6 3/4 Business envelope has a width of 6.5 inches and a height of 3.625 inches, giving it a total surface area of 23.56 square inches. Its maximum enclosure size is 3.375 x 6.25 inches. This envelope is also referred to as the 6-3/4 envelope, corresponding to its height dimension.
Like the #6 envelope, the #6 3/4 gets its numbering from William Irwin Martin's late 19th century system for standardizing envelope sizes. The "3/4" indicates this envelope is slightly larger than the basic #6 size. The added height makes the #6 3/4 well-suited for holding documents and inserts that require just a bit more space than a standard #6. It strikes a nice balance of being compact yet roomy. Today the #6 3/4 remains popular for commercial mailings such as brochures, flyers, invoices and statements. Its versatility makes it useful for both transactional and advertising mail.