Envelopes are available in many different sizes. Each size is referred to by a number. The most common ones are listed below.
- #6 1/4 – 3 1/2″ x 6″
- #6 3/4 – 3 5/8 x 6 1/2″
- #7 – 3 3/4″ x 6 3/4″
- #7 3/4 – 3 7/8″ x 7 1/2″
- #8 5/8 – 3 5/8″ x 8 5/8″
- #9 – 3 7/8″ x 8 7/8″
- #10 – 4 1/8″ x 9 1/2″
- #11 – 4 1/2″ x 10 3/8″
- #12 – 4 3/4″ x 11″
- #14 – 5″ x 11 1/2″