Sudoku Maker

How to make a printable sudoku

1. Pick the grid. 4×4 uses the numbers 1–4 in four 2×2 boxes, the usual first sudoku for children of about 4 to 7. 6×6 uses 1–6 in six boxes of 2 rows by 3 columns. 9×9 is the classic newspaper puzzle with nine 3×3 boxes.
2. Pick the difficulty. It is set by the reasoning a puzzle needs, not by guessing from the number of clues (see the questions below).
3. Choose what goes in the squares: numbers, the letters of a word or a name, or pictures (heart, star, ball, triangle, tree, moon, diamond, square and plus, in colour). Letters and pictures get a key line at the top of the page that shows the set to use.
4. Choose 1, 2, 4 or 6 puzzles per page. One per page gives big squares for small hands (a 4×4 square is over 4 cm); six 9×9 puzzles per page still give squares of about 8 mm, enough for a sharp pencil.
5. Add a title or a name if you like, then press Download PDF and print at 100% (“Actual size”). The answers are on the last page, so you can print the puzzle pages and keep the answers back.

Press New puzzles for a different set with the same settings. Each set has a number (in the page footer); the same number with the same settings always gives the same puzzles, so a teacher can make a second copy of a sheet later.

Questions

Is this a free printable sudoku maker?

Yes. There is no sign-up, no watermark and no limit. The puzzles are made by your own browser, so nothing is sent anywhere, and it works on a phone. Every download is an A4 or US Letter PDF (browsers set to US or Canadian English start on Letter) with 12 mm margins, so home printers do not clip the grid, or a 300 dpi PNG of the page shown if you want to put it in a worksheet or print it from a photo app.

How is the difficulty chosen?

Each puzzle is solved by a step-by-step solver that only uses the methods a person uses, and the puzzle is kept only if it needs the methods of its level:

• Easy can be finished with naked singles alone: at every step some square has only one number left that fits its row, column and box. Easy 9×9 puzzles also keep 36 of the 81 numbers.
• Medium needs hidden singles (a number that fits in only one square of a row, column or box) or pairs (two squares in a group that can only hold the same two numbers), and nothing harder. A medium 9×9 usually has 23 to 27 clues.
• Hard cannot be finished with singles and pairs at all; it needs a pointing pair, a box/line reduction, a triple or a longer chain of reasoning, and it still has only one answer. Hard puzzles have no clue that could be removed without giving a second answer.

One honest exception: on a 4×4 grid, every puzzle with a single answer can be solved by naked singles (we checked 7,878 random ones), so there the levels differ by the number of clues: 8 for Easy, 6 for Medium and the fewest possible, 4 or 5, for Hard.

How do I make a 6×6 sudoku?

Choose 6×6. Each row, column and 2×3 box (two rows tall, three columns wide) holds 1 to 6 once. It is the natural step between 4×4 and 9×9: an easy 6×6 keeps 16 of its 36 numbers, a medium one about 10. A 6×6 sheet of four puzzles is a good size for ages 6 to 10.

Can I make a sudoku with letters, or with my child’s name?

Yes. Choose Letters and type a word with as many different letters as the grid has: 4 for a 4×4 (MILO, ROSE, SNOW), 6 for a 6×6 (SLEIGH, CASTLE, MAGNUS), 9 for a 9×9 (SNOWFLAKE, CHIPMUNKS). Every letter has to appear exactly once in each row, column and box, so a word with a repeated letter cannot work: EMMA or ANNA are refused and the page says which letter repeats. A name with a repeat can often be swapped for a nickname, or use pictures instead.

Can a child solve one on the phone?

Yes. Press Solve here: the first puzzle of the sheet appears as big squares. Tap a square, then tap a number, letter or picture under the grid; tap Clear to empty it. A clash with the same symbol in the row, column or box turns red, and the grid turns green when it is all correct. Nothing is saved or sent.

Does every puzzle really have only one solution?

Yes. Every clue is removed only after an exact solver has checked that the puzzle still has exactly one answer, and the printed answer page is that answer. Our test checks 40 puzzles of every size and level with a second, independent solver each time the tool changes.

How does the booklet work?

Tick Make a booklet with a cover and choose 1 to 20 sheets. The PDF starts with a cover (your title, the “for” line and the number of puzzles), then the sheets, then all the answers, up to 12 to a page. Twenty sheets of six puzzles is 120 puzzles; a hard 9×9 booklet of that size takes about 3 seconds on a laptop and can take 10 or more on an older phone; the button counts up while it works. Print it double-sided and staple it at the side, or put the pages in a folder.