An A7 envelope typically measures 5.25 x 7.25 inches (5 1/4" x 7 1/4").

Quick Scoop

If you’re holding a standard 5" x 7" invitation or greeting card and wondering what to mail it in, the usual match is an A7 envelope, which is made just a bit larger so the card slides in comfortably without bending. It’s one of the most common invitation sizes used for weddings, parties, and holiday cards in the US.

For a mental picture: imagine a typical photo-print–style invite; the envelope is just slightly taller and wider, giving a clean border and enough room for thicker card stock.

TL;DR: A7 envelope size = 5.25" x 7.25" (about 133 x 184 mm) , ideal for 5" x 7" cards.

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