Every puzzle here can be finished by reasoning
That sentence is doing more work than it looks like it is, so it is worth being precise about what it means and why almost nobody else says it.
When you press Build the sheet, the puzzles are generated in your browser, and each one is then handed to a solver that knows only the techniques a person can say out loud: naked and hidden singles, naked and hidden pairs, pointing pairs, box and line interactions, X-Wing. The solver never falls back on searching. If it cannot finish a board with those techniques alone, that board does not go on your sheet.
On a screen this would be a nicety. On paper it is the whole thing. There is no hint button on a printed sheet, no undo, and no way to check whether the digit you just wrote in ink was right. A puzzle that quietly requires guessing does not feel like a hard puzzle. It feels like forty minutes of careful work followed by a contradiction, and no way to tell which of your last twenty entries caused it.
One solution is not the same as solvable by logic
This is the most common misunderstanding in sudoku, and it is repeated confidently almost everywhere, including by people who make puzzles.
Nearly every sudoku generator works the same way: fill a complete grid, then remove digits one at a time, checking after each removal that the puzzle still has exactly one solution. That check is real and it matters. It is also a check about uniqueness, and uniqueness says nothing about whether a human being can get there.
A grid can have exactly one solution that no known human technique will ever reach. The digits are determined, in the sense that only one arrangement works, but no chain of reasoning available to a person exposes them. The only way through is to pick a cell, assume a digit, follow the consequences for twenty moves, and find out whether the grid falls apart. That is not a technique. It is trial and error with extra steps.
We know precisely how common this is, because we measured our own puzzles before we fixed it. 47 percent of our expert boards had exactly one solution and no logical path to it. The uniqueness check had passed on every single one. Every one of them would have printed perfectly happily.
Once you know the distinction, you start noticing who is quiet about it. Some of the best known printable sudoku sites are refreshingly straight: one describes its hardest tier as puzzles that cannot be solved without making guesses, and another lists trial and error among the techniques for its top level. Most say nothing at all, which is not the same as it not happening.
What each level actually asks of you
Difficulty labels usually describe how empty a grid is, which is a proxy for how long it takes rather than how hard it is. A board with sixty blanks that yields entirely to singles is a long puzzle, not a difficult one. Ours are labelled by the hardest technique they genuinely require, measured by the same solver that checks them.
Easy can be finished with naked singles alone. You look at a cell, work out which digits its row, column and box have already used, and find that only one is left. No notation needed, nothing to remember between glances. This is the level for beginners and for children.
Medium adds hidden singles: rather than a cell with one candidate, you look for a digit with one home. Somewhere in this box, the 7 has only one square it can occupy, even though that square could hold several other digits too. It is a different way of looking and it is the first real technique most people learn.
Hard requires pairs and the interactions between a box and a line. Two cells in a row that can only hold 3 or 8 between them: you cannot say which is which, but you can rule 3 and 8 out of every other cell in that row. This is where pencil marks start earning their keep.
Expert is the same family of reasoning over a much emptier grid, where more of the work is holding possibilities in your head at once. We are honest about the ceiling: a board that genuinely requires an X-Wing turns up perhaps twice in a hundred, so expert means the hardest reasoning available rather than a guarantee of an exotic pattern every time.
Mixed ramps from easy to expert across the sheet, which suits a set you plan to work through over several sittings. It ramps rather than shuffling on purpose: a random order means the second puzzle can stop you dead.
Sizes, paper and pencils
The sheet sets orientation only and leaves the paper to your printer, so A4 and US Letter both work without scaling. Every layout is sized against the shorter of the two, with room to spare, which is why nothing spills onto an unexpected extra page.
1, large gives one puzzle per sheet with cells around 18mm across. That is genuinely large print: room for a pen, and room to pencil candidate digits into a corner without them becoming unreadable. If you are printing for someone whose eyes have opinions, or for a child still learning to write small, this is the one.
2, medium is the size you know from puzzle magazines and newspapers, and it is the best balance of paper and comfort for most people.
4, compact puts four to a sheet. Fold it twice and it goes in a pocket, which is the right format for a train, a waiting room, or a flight.
Answers
Answer pages come at the end, six to a page, numbered to match the puzzles they belong to. They are printed as complete grids rather than as strings of digits, so checking a single square does not mean counting along a row of eighty one numbers to find your place.
If the sheet is a gift, or homework, or something you would rather not be tempted by, the checkbox turns them off entirely.
Who these are for
Teachers get a fresh set every time the button is pressed, so a class of thirty can each have a different puzzle at the same difficulty. That makes copying from a neighbour pointless, and it means next term does not need a new source.
Anyone printing for a parent or grandparent should start with easy or medium at the large size. The large layout exists for exactly this, and the no-guessing guarantee matters more here than anywhere: an unsolvable puzzle reads as your own failing rather than the puzzle's.
Travellers want the compact layout. Paper needs no battery, works between the gate and the runway, and cannot show you a notification.
And a good number of people simply want an hour away from a screen. A pencil and a sheet of paper are unusually good at that.
If the printout comes out wrong
Almost every printing problem with a sheet like this comes from one of four settings, and all four live in your browser rather than on this page.
The grid prints small with wide white borders. Your print dialog is scaling to fit. Set scale to 100 percent, or to Default rather than Fit to page. The sheet already leaves proper margins, so scaling it down only shrinks the cells you have to write in.
The page carries a URL and a date. Those are browser headers and footers. In Chrome, open More settings in the print dialog and clear the Headers and footers checkbox. Safari has the same control under File then Print, and Firefox keeps it in Page Setup under Margins and Header/Footer.
The grid lines look pale or uneven. Some printers economise on light greys in draft mode. The thick lines that divide the nine boxes are printed near black precisely so they survive this, but if the thin lines are fading, switch off draft or economy mode. Nothing on the sheet uses a background fill, so you do not need the Print backgrounds option turned on.
You get one blank page, or one page more than you expected. Press Build the sheet before printing, since there is nothing on the page until you do. A single extra page at the end is usually the answer key, which is six puzzles per sheet and so does not divide evenly into every set size.
New to sudoku? Here is enough to start
If you are printing these for somebody else and they ask how it works, the whole game fits in one sentence: fill the grid so that each row, each column and each of the nine three by three boxes contains the digits 1 to 9 exactly once. Nothing is added, nothing is multiplied, and no arithmetic is involved at any point.
The first technique is the one every solver starts with. Pick an empty cell and look along its row, down its column, and around its box. Cross off every digit you can already see. If exactly one digit survives, it belongs in that cell. That is a naked single, and an easy sheet from this page can be finished with nothing else.
The second technique is the mirror image of the first, and it is where most people feel sudoku click. Instead of asking what a cell can hold, take one digit and one box, and ask where that digit can go. Often several cells look possible at a glance, but once you account for the rows and columns feeding into that box, only one square is left. That is a hidden single, and it is what the medium sheets are built around.
Those two carry you a long way. When you want the rest, the rules and techniques page covers pairs, pointing pairs and the box and line interaction with worked examples.
Frequently asked questions
Are these printable sudoku puzzles really free?
Yes. No sign-up, no watermark, and no limit on how many sheets you print.
Can every puzzle be solved without guessing?
Yes, and it is checked before printing rather than assumed. A board the solver cannot finish by reasoning never reaches your sheet.
Does one solution mean a puzzle can be solved by logic?
No. Uniqueness and solvability are different properties, and the gap between them is where unfair puzzles come from. See the section above.
Can I print large print sudoku?
Choose 1, large. One puzzle fills the sheet with cells about 18mm across.
Does this work on US Letter as well as A4?
Yes. The sheet leaves the paper size to your printer and fits both.
How do I remove the URL and date from the printed page?
They come from your browser, not the sheet. In Chrome, open More settings in the print dialog and clear the Headers and footers box.
Why does the expert set take longer to build?
Because each board is generated and then tested, and boards that demand the hardest reasoning have to be sampled for. Twenty four expert puzzles take around twenty seconds. Easy and medium are instant.
Can I print only the answer pages?
The answers are always the last pages, so enter just those page numbers in your print dialog.
Want to solve on a screen instead? Play sudoku online, or read the rules and techniques first.