How to print sudoku puzzles that look right

A printed sudoku beats a screen: you can see all your pencil marks at once, scribble freely and leave the sheet on the kitchen table for a week. A bad print loses those advantages, with grids too small to annotate, box borders you cannot tell from the cell lines, or a page clipped at the edge. Four settings fix most of that.

Match the page size to your paper, before you generate

A4 measures 210 × 297 mm and US Letter 216 × 279 mm, so Letter is wider and shorter. The difference is small, but if you print an A4 layout on Letter paper, the printer either scales everything down or crops the bottom, and either way you lose grid size.

Pick the right size in the generator instead of fixing it in the print dialog. The generator lays the page out at your chosen size with 16 mm margins on all four sides, inside the printable area of common home and office printers, so you have nothing to adjust afterwards.

Print at 100% instead of “fit to page”

Scaling spoils more prints than any other setting. “Fit to page”, “shrink oversized pages” and “scale to fit” exist to rescue documents with margins that are too tight. The PDF from this site has room to spare, so the setting shrinks the grid by a few percent for nothing, and you notice the loss when you write three candidate digits into a corner.

In most print dialogs the option you want is Actual size or 100%. Check it each time, because some printer drivers reset to fit-to-page on their own.

Choose puzzles per page for how you solve

The layout sets your grid size, and the grid size decides how comfortable the puzzle is. On A4 with standard margins, one puzzle per page gives about a 17 cm grid, two give about 12 cm, four about 8 cm and six about 6.5 cm.

If you solve without candidate marks, six per page works and saves a lot of paper. If you pencil in candidates, which you will need above medium, you need cells of about 12 mm to write three small digits legibly, and that means two per page. For expert grids, where you end up marking nearly every empty cell, one per page is worth the paper.

A reasonable default: easy and medium at four per page, hard at two, expert at one.

Keep the answer key separate

If you print for other people, the placement of the answers matters. The PDF puts the whole answer key in its own section after the puzzles, on separate sheets, so you can hand out the front half and keep the back. Each solution carries the same six-character code as its puzzle, so you can split the pages up and match them later. If the key goes missing, the same code fetches the answer on the answer lookup page.

To leave the answers out, untick the option before generating, or print only the first half of the document, since the key comes last. The printable sudoku with answers page explains the key in more detail.

Paper and ink

Ordinary 80 gsm copier paper works, and most people use it. If you press hard with a pencil or plan to erase a lot, 90 to 100 gsm paper holds up better, because erasing on thin paper leaves a grey smear that makes candidate marks hard to read.

Print in black and white, in draft or economy mode. The grids are line work with no shading, so draft quality looks the same and uses about half the ink. Skip colour and photo settings, which print slower and give the same result.

On a printer you have not used for sudoku before, print a single page first. Check that the box borders look heavier than the cell lines, that the digits are crisp and that nothing is clipped. Then send the other nineteen pages.

Printing for a group

For a classroom, a care home or a long journey, generate one batch instead of several. A run of 24 puzzles at four per page fills six sheets, or three double-sided, plus the same again for the key. Consider mixing difficulties: tick more than one level and the generator splits the run evenly across them, easiest first. A mixed set keeps a room of different abilities moving at about the same pace.

The generator makes fresh puzzles each run instead of pulling them from a fixed library, so two people printing on the same day get different grids, and you can run off a second set for a second group without anyone recognising it. Set your run and print it.