Announcement envelopes, also called A-style, are popular for stationary, invitations and announcements. A-2 envelope dimensions are 4.375 inches by 5.75 inches or 4 3/8 inches by 5 3/4 inches.
The compact size of A-2 envelopes helps to minimize waste. Internal cards cut from a standard 8.5-inch-by-11-inch sheet of paper or card stock easily fit in them as a four-up design, meaning four of the same design on one side, or a two-up folded design, meaning two of the same design folded. The exact enclosure area varies depending on the thickness of materials, but suggested dimensions for enclosures are 4.25 inches by 5.5 inches.