Printable Sudoku Puzzle Generator

A classic sudoku puzzle uses a 9×9 grid divided into nine 3×3 boxes (also called regions or blocks). The grid starts with some numbers already filled in — these are your clues. Your goal is to fill every empty cell so that:

• Every row contains the digits 1 to 9 exactly once.
• Every column contains the digits 1 to 9 exactly once.
• Every 3×3 box contains the digits 1 to 9 exactly once.

No arithmetic is involved — the puzzle is solved entirely through logical deduction. You eliminate possibilities until each cell has only one digit that can legally go there. Every puzzle generated here has exactly one valid solution.

1. Choose a Level — Very Easy, Easy, Moderate, Hard, or Very Hard.
2. A new puzzle appears automatically. Click Create for another puzzle at the same level.
3. Click Show Solution to reveal all the numbers and verify the puzzle.
4. Click Download to save a PDF with 4 puzzles, with an optional answer key page.

Difficulty is controlled by the number of starting clues — the digits already printed on the grid. Fewer clues means more empty cells and longer chains of deduction.

Level	Starting clues	Empty cells	Best for
Very Easy	51 – 53	28 – 30	First-time solvers, young students (Grade 3+)
Easy	37 – 50	31 – 44	Casual players, Grades 4 – 5 classrooms
Moderate	32 – 36	45 – 49	Regular solvers, logic enrichment (Grade 6+)
Hard	27 – 32	49 – 54	Experienced players, gifted learners
Very Hard	20 – 26	55 – 61	Expert solvers, advanced logic challenge

For classroom use, Very Easy and Easy work well as warm-up activities or early finisher tasks. Moderate suits homework sets where students work independently. Hard and Very Hard are best as enrichment challenges or puzzle club material.

If you enjoy the pure logic of sudoku and want a harder version that adds arithmetic, try Sum Sudoku — it prints sum clues around the grid edges — or Calcudoku, where caged regions must hit a target number using a given operation.

Every sudoku can be solved with logic alone — no guessing needed on Well-formed puzzles. These three techniques cover the vast majority of cells in Easy through Hard puzzles.

1. Naked Single

Look at an empty cell and list which digits are already present in its row, its column, and its 3×3 box. If only one digit from 1 to 9 is not blocked by any of those three constraints, that digit must go in the cell. This is the most common move in Very Easy and Easy puzzles — scan every empty cell until you find one.

2. Hidden Single

Pick a digit (say, 7) and pick a row. Check every empty cell in that row: can 7 go there without clashing with its column or box? If only one cell in the row can legally hold a 7, place it there — even if that cell could also hold other digits. Repeat the same check for columns and boxes. This technique unlocks most Moderate-level puzzles.

3. Cross-Hatching (Scanning)

For a 3×3 box, pick a digit and look at the rows and columns that already contain it elsewhere on the grid. Those rows and columns are blocked — the digit cannot appear in them again. The remaining empty cells in the box, after eliminating blocked rows and columns, are the only candidates. If exactly one candidate cell survives, place the digit there.

Practical tips

• Start with the most constrained cells — rows, columns, or boxes that are nearly full are easier to complete.
• Use pencil marks — lightly write all candidate digits in a cell's corner, then cross them off as neighbours are filled.
• Work the easiest digit first — whichever digit appears most often on the starting grid leaves fewer empty cells to resolve.
• If you are stuck, lower the difficulty one step; Very Hard puzzles require advanced techniques (pairs, triples, X-wings) beyond the scope of beginner solving.

Once Hard puzzles feel comfortable, the natural next step is a variant that layers arithmetic on top of the same grid logic. Sum Sudoku adds sum clues at the borders of each 3×3 region, while Calcudoku replaces the fixed boxes with irregular cages and target calculations — both reward the same systematic elimination thinking you have already built. For a division-focused twist, try Divide Sudoku.

The generator supports two paper sizes and two puzzle-per-page layouts. The default is 4 puzzles per page in a 2×2 grid — compact and efficient for classroom sets. Switch to 1 puzzle per page for a full-size grid with larger cells, better suited to pencil-marking candidates (Hard/Very Hard levels), accessibility needs, or younger students who need more room to write.

In 1-per-page mode the PDF contains 4 pages (one puzzle each). If you tick "Solution page", one extra page is added at the end with all 4 solved grids printed together.

• A4 (210 × 297 mm) — the default in Europe, Australia, and most of the world. Select this if your printer's default tray is loaded with A4.
• Letter (8.5 × 11 in / 216 × 279 mm) — the standard in the United States and Canada. Select this for North American printers.

Recommended print settings: scale at 100 % (or "actual size") — do not use "fit to page" or "shrink to fit", which can reduce the cells to a size that is hard to write in. Print in portrait orientation. Black and white is fine; no colour ink is needed.

Each cell on a printed A4 worksheet is approximately 13 × 13 mm — large enough for a digit written with a standard pencil. If you are printing for younger students or anyone with larger handwriting, scale up to 110–120 % and trim the margins.