One card per line
The card box takes front | back, one card per line. A tab divides just as well as the pipe character, which matters more than it sounds: select two columns in a spreadsheet, copy, paste here, and every row lands correctly split without touching a single line. If a back contains its own pipe, only the first one is treated as the divider and the rest stays in the text, so deliberate | on purpose | unhurried keeps both meanings on the back of one card. A line with no divider at all cannot be split into two sides, so it is skipped and listed underneath the results. Leaving the back empty is allowed and prints an em dash, which reads as deliberate rather than as a printing fault.
Picking a card size
| Size | Per sheet | Suits |
|---|---|---|
| Business card 3.5 x 2 in | 10 | A term and a short definition. Fits a card wallet, a binder ring, a shirt pocket. |
| Index card 3.5 x 2.5 in | 8 | Two or three lines of text, or room to annotate in pen later. |
| Half index 3.75 x 5 in | 4 | Full sentences, a formula, space to sketch the thing you are trying to remember. |
All three print onto plain letter paper with dashed cut lines. Card stock around 65 lb or heavier stops the cards curling after a week of shuffling, and it is the single change that makes home-printed cards feel like bought ones. Anything much heavier than 110 lb will jam a lot of consumer printers on the second pass, which is the pass you cannot afford to lose.
Duplex versus fold
The duplex document alternates: fronts, backs, fronts, backs. Each back page has its rows reversed left to right before printing, because turning a sheet over on its long edge swaps left and right. Pre-mirroring is what makes card 3 come out behind card 3 rather than behind card 4. If your printer flips on the short edge instead, everything arrives rotated and offset by a column, and no amount of re-feeding fixes it — change the setting. Card numbers appear only on the fronts, on purpose: a numbered side is a front, and that alone sorts out a dropped stack.
The fold document prints on one side. Each cell holds the front at the top and the back inverted at the bottom, so cutting vertically and folding backward at the dotted line gives a two-sided card that cannot be out of register with itself. It uses more paper — a business-card deck fits 4 to a sheet folded against 10 duplex — and that is the whole trade. If you are printing at a shared office machine whose duplex settings you do not control, print the fold layout and stop thinking about it.
Font stepping, numbering, shuffling
With automatic sizing on, each face is measured by character count and dropped through six steps: six characters or fewer print largest, over ninety print at about a third of that. Sizing per face rather than per deck means a one-word front stays readable across a table while a long definition still fits its cell. The measure is character count and nothing else, so text with several forced line breaks, or wide glyphs, can still overrun. When it does, turn stepping off and move up a card size rather than fighting it.
Shuffling is seeded by the number in the last field. The same number always yields the same order, so printing the fronts today and the backs tomorrow still lines up, and a reprint of a lost sheet matches the cards you already cut. Change the number and you get a different order from the same deck — useful when you have learned the sequence rather than the content, which happens sooner than most people expect and is the main reason a deck stops working.
Questions people ask
The backs printed behind the wrong cards.
Almost always the duplex flip setting. This document assumes flipping on the long edge and has the backs pre-mirrored to suit. If your driver is set to short-edge flip, the sheet comes out inverted and shifted by a column. Change it and reprint two test sheets. If you are feeding by hand, turn the stack over without rotating it — left edge stays on the left. When neither works, print the fold layout, which has no second pass to get wrong.
Can I fit more cards on a page?
Business card size already puts 10 on a letter sheet, which is close to the practical limit. Denser grids make the text small enough that reading a card at arm's length stops working, and they multiply the cutting. Past a few hundred cards, splitting the deck across runs is faster than shrinking it.
Are my cards saved anywhere?
No. The layout and both print documents are assembled in the page and a refresh empties everything. Keep the text copy in a note or a file if you want to come back to it — the format it produces is the format it reads, so pasting it back in reconstructs the deck exactly.