Sudoku Generator

What you can do with the Sudoku Generator

This generator builds printable PDF worksheets of classic 9×9 Sudoku puzzles. Each page holds six puzzles laid out in a two-column grid. You can print puzzle pages alone or add a matching solution sheet at the end. Teachers use it for classroom warm-ups, parents print a week of puzzles for car journeys, and puzzle enthusiasts keep a stack ready for morning coffee.

Every puzzle starts from a fully solved grid, then removes clues according to your chosen difficulty. The algorithm shuffles row bands, column stacks, and the digit mapping so no two grids are identical. You'll never see the same board twice, even if you generate thousands.

What you can customise

• Difficulty — easy (40–45 clues), medium (32–38), hard (24–30), expert (17–23), or mixed (random draw from easy, medium, and hard for variety).
• Safe mode — when enabled, the generator solves each puzzle internally and discards any board with multiple solutions, guaranteeing a single logical path.
• Paper size — A4 or US Letter; the grid scales to fit either format without clipping.
• Solution sheet — toggle on to append a second page showing completed grids for all six puzzles.
• Count — defaults to six puzzles (one page), but you can request more to build multi-page workbooks.

How to use the tool

1. Pick your difficulty level from the dropdown. Choose mixed if you want each of the six puzzles on the page to draw a random difficulty.
2. Turn on safe mode if you're preparing puzzles for a competition or classroom test where a unique solution matters.
3. Select A4 or US Letter to match your printer and regional paper stock.
4. Tick the solution-sheet checkbox if you want answers on a separate page at the end.
5. Click Generate. Your browser will download a branded PDF with six puzzles per page and optional solutions.
6. Print the PDF and hand out copies, or keep it on your tablet for screen solving.

Who this Sudoku generator is for

Teachers and tutors

Print a set for each student at the start of a logic unit, or use them as timed exercises to track progress. The six-per-page layout means fewer sheets to photocopy and simpler distribution.

Parents and homeschoolers

Generate a week of puzzles on Sunday evening, then hand your child one puzzle each morning as a brain warm-up. Mix difficulty levels to match their current skill without hunting through puzzle books.

Puzzle enthusiasts

Keep a rotating supply of fresh puzzles. Safe mode ensures you won't waste time on ambiguous boards, and the solution sheet lets you check your work without typing the grid into a web solver.

Worked classroom example

A Year 7 maths teacher wants to introduce Sudoku during the final ten minutes of Friday lessons. She selects medium difficulty and safe mode, chooses A4 paper, and enables solutions. She clicks Generate and prints thirty copies—one per student. Each sheet has six puzzles, so that's six weeks of Friday warm-ups from a single print run. She files the solution page separately and uses it to spot-check students who finish early. Because the layout is consistent, students know exactly where to write their answers and don't waste time deciphering cramped grids.

How the generator works under the hood

The algorithm starts by building a valid completed Sudoku grid using a deterministic base pattern, then shuffles row bands, column stacks, and digit assignments with a seeded random-number generator. Once the solution exists, the code removes clues one by one until it hits the target count for your chosen difficulty. In safe mode, an internal backtracking solver checks that exactly one solution remains; if the puzzle becomes ambiguous, the generator discards it and tries a new removal order. This two-pass approach is slower but guarantees logical solvability.

Designed for A4 and US Letter printing

The PDF renderer scales the grid and text to fit both A4 (210×297 mm) and US Letter (8.5×11 in) without clipping or leaving awkward margins. Pick your region's standard paper size from the dropdown and print directly from the browser; no manual zoom or layout tweaks required. The six-puzzle-per-page layout keeps ink usage reasonable while offering enough variety for a full sitting.

Notes and limitations

• Mixed difficulty draws only from easy, medium, and hard; expert is excluded from the random rotation to avoid frustration when users expect moderate challenge.
• Safe mode can take a few extra seconds per puzzle because the solver must confirm uniqueness; disable it if you're printing hundreds of puzzles and speed matters more than guarantee.
• The generator does not support 4×4 or 16×16 variants, diagonal Sudoku, or custom clue placements—it's classic 9×9 only.
• There is no option to save a specific puzzle by seed or ID; each generation is ephemeral, so print or download immediately if you want to keep a particular set.