Folded card sizes: what each sheet makes and which envelope fits

Every folded card is a fixed fraction of the paper it is printed on. A half-fold card is the sheet folded once, so the card is half the sheet. A quarter-fold card is folded twice, so the card is a quarter of the sheet and everything, front, inside and back, prints on one side. ISO paper sizes halve neatly: A4 folded once is A5, and folded twice is A6.

That means you choose the card size by choosing the sheet. To get a bigger card from a home printer you need a bigger sheet, and to get a 5 × 7 in card you need paper that is twice that size, 10 × 14 in, which few home printers take. That is why home-printed cards are usually A6 or 4.25 × 5.5 in.

Quarter fold, printed on one side: A4 (210 × 297 mm) gives an A6 card of 105 × 148 mm; US Letter (8.5 × 11 in) gives 4.25 × 5.5 in, about 108 × 140 mm; A3 gives an A5 card of 148 × 210 mm, if your printer takes A3. Half fold, printed on both sides: A4 gives an A5 card; Letter gives 5.5 × 8.5 in.

The popular US sizes come from cut sheets rather than folding a standard page. A 5 × 7 in folded card is a 7 × 10 in sheet folded once; a 4 × 6 in folded card is a 6 × 8 in sheet. You can print them on Letter and trim the waste, but then the card is a half fold and needs the inside printed on the back of the sheet.

Envelopes are sized to leave a few millimetres around the card. An A6 card fits a C6 envelope (114 × 162 mm), an A5 card fits a C5 (162 × 229 mm), and DL (110 × 220 mm) suits a long card made from an A4 sheet folded in three. In the US, a 4.25 × 5.5 in card fits an A2 envelope (4.375 × 5.75 in), a 5 × 7 in card an A7 (5.25 × 7.25 in) and a 4 × 6 in card an A6 envelope (4.75 × 6.5 in).

If you do not have an envelope to hand, Foldpic's gift kit prints a matching envelope sized to your card, with fold lines and glue strips, plus gift tags and a paper sleeve, as a separate PDF in the same colours as the card.

For a home printer, the quarter fold is the easy choice: one sheet, one side, no duplex alignment, and an A6 or 4.25 × 5.5 in card that fits standard envelopes and costs one stamp. It is the format Foldpic uses for its birthday, thank-you, invitation and just-because templates.

Choose a half fold when you want a larger card and your printer duplexes well, or when you print on card that is too stiff to fold twice. Anything over about 250 gsm resists a second fold, so for very heavy card a half fold, scored first, gives a cleaner result.