Envelope Size for a Card Calculator
Find the envelope size a card actually needs — the right clearance around a folded card — and see which standard envelope fits.
How it works
Envelope width = card width + clearance · Envelope height = card height + clearance
An envelope has to be a little larger than the card in every direction, or the card jams going in and creases coming out. A 5 mm allowance all round is snug and neat; 8 mm slides easily; 12 mm suits a thick or padded card. Matching that minimum to the nearest standard size (A6, A7, C6 and friends) saves you buying custom envelopes.
Worked example
A folded 127×178 mm card (a 5×7 photo card) with snug 5 mm clearance needs an envelope of at least 132×183 mm. The A7 / 5×7 envelope at 133×184 mm is the smallest standard that clears it.
Frequently asked questions
How much bigger than the card should the envelope be?
About 5 mm larger on every side for a snug fit, 8 mm for easy insertion, and 10–12 mm for a thick or embellished card. Too tight and the card creases; too loose and it slides around in the mail.
What is an A7 envelope?
A7 (also sold as a 5×7) is about 133×184 mm inside and is the standard envelope for a folded 5×7 inch photo or greeting card. It is one of the most common invitation and card sizes.
Should I measure the card flat or folded?
Folded — the envelope holds the card at its finished size. Measure the folded width and height, which for a standard card is half the flat sheet in one direction.
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This calculator is for educational purposes. Double-check important results before acting on them.