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Sudoku Generator
Generate Sudoku puzzles in 4×4, 6×6, or classic 9×9 sizes. Kid-friendly beginner puzzles to challenging classics with solutions included.
How to Play Sudoku:
Fill in the grid so that every row, column, and box contains the numbers 1 to 4. Each number can only appear once in each row, column, and box.
Select your options and click
"Generate Sudoku" to create a puzzle
The Sudoku Generator creates logic puzzles at multiple difficulty levels and grid sizes. Start with 4×4 puzzles for young learners (using numbers 1-4), progress to 6×6 for intermediate challenge, or tackle the classic 9×9 grid. Sudoku develops logical thinking, pattern recognition, and problem-solving skills without requiring any math calculation—just logic! Each puzzle includes a solution key for checking work.
A sudoku generator that makes a fresh puzzle every time
Pick a grid size, pick a difficulty, and press generate. The puzzle is built from scratch in your browser each time you click, so you are never working through the same twenty puzzles a printable PDF pack gives you. Press New Puzzle and the whole board is different.
Every puzzle starts as a complete, valid solution. Numbers are then removed one at a time, and after each removal the board is checked to make sure exactly one answer still fits. If taking a number out would leave two possible answers, it goes back. That is what separates a real sudoku builder from a grid with random blanks in it: the puzzle can always be reasoned out, never guessed at.
The solution is generated alongside the puzzle, so the answer key is ready before you have finished reading the instructions. Switch between the Puzzle and Solution tabs to see either one.
4x4, 6x6, and the classic 9x9 grid
The 4x4 sudoku is where most children start. It uses only the numbers 1 to 4, and the boxes are 2x2, so a five or six year old can hold the whole board in their head at once. A mini sudoku 4x4 is usually solvable in two or three minutes, which is about the right length for a warm-up or a bus ride.
The 6x6 grid sits in the middle, with numbers 1 to 6 and rectangular 2x3 boxes. Those wider boxes are the useful part: children who have only seen square boxes have to think about what a box actually means rather than pattern-matching on shape. It is a good step up before the full-size board.
The 9x9 is the classic, with 3x3 boxes and numbers 1 to 9. Same rules, more room to make a mistake. Anyone comfortable with 6x6 can move to 9x9 on easy and work up from there.
What easy, medium, and hard actually change
Difficulty here means how many numbers are taken away. On a 9x9 board, easy removes around 35 cells and leaves you roughly 46 givens, medium removes about 45, and hard removes about 55, leaving only a couple of dozen starting numbers. On a 4x4 the range is 6 to 10 removed cells, and on a 6x6 it runs from 14 to 22.
More blanks means fewer places where a number is forced immediately, so you spend longer scanning rows and columns before anything falls into place. It does not mean the puzzle needs a harder technique. Every puzzle still has one answer reachable by elimination, so a hard 9x9 is a longer sit rather than a different kind of thinking.
If a class is mixed, generating the same grid size at two difficulties is the simplest way to differentiate. The sheets look identical on the desk, which matters more to children than adults tend to expect.
Printing, answer keys, and saving as an image
Print Puzzle opens a clean print sheet with the title you typed, the grid size and difficulty underneath, a line of instructions naming the box shape for that size, and Name and Date lines at the bottom for classroom use. Nothing from the website itself comes along except a small line noting where it was made. Margins are set for standard paper, and A4 works if you let the printer scale to fit.
To print the answer key, switch to the Solution tab first and print from there. The sheet is titled as an answer key, the numbers you were given stay black and bold, and the ones that were blanked out print in green, so marking a stack of sheets is a matter of comparing colours rather than reading every cell. The Name and Date lines are left off the key.
Download Image saves the preview as a PNG at double resolution, which is the easier route if you are putting a puzzle into a worksheet, a slide, or a newsletter rather than printing it directly. Five colour themes are available for the grid lines and shaded given cells: classic grey, ocean, forest, sunset, and lavender.
Using sudoku with children
There is no arithmetic in sudoku. The numbers are just four, six, or nine distinct symbols, and you could play with letters or shapes and lose nothing. That is why it works for children who find maths worksheets discouraging: the skill being practised is elimination, keeping track of what is already ruled out, and noticing when only one option is left.
The first technique worth teaching is scanning. Pick a number, look at the rows and columns it already appears in, and find the box where only one empty cell is left for it. That alone solves most easy puzzles. Once that stops being enough, the next move is working cell by cell instead of number by number: look at one empty square, list what its row, column, and box have already used, and see what survives.
Pencil is worth insisting on. Writing small candidates in the corner of a cell is how the puzzle gets solved without guessing, and it is much easier to teach that habit on a 4x4 grid where there are only ever four candidates to write down.
Frequently Asked Questions
Does every puzzle have only one solution?
Yes. As numbers are removed, the board is re-checked each time, and any removal that would allow a second valid answer is undone. So the puzzle you print can be solved by logic alone, with no point where you have to guess and backtrack.
What is a good sudoku for kids who have never played?
Start with a 4x4 on easy. It uses the numbers 1 to 4, has 2x2 boxes, and leaves ten of the sixteen cells filled in, so the first few moves are usually obvious. Once that feels quick, move to 4x4 hard, then 6x6.
Can I print the answer key?
Switch to the Solution tab and use the print button there. The key prints with the original given numbers in black and the answers in green, and it is labelled as an answer key in the heading.
How many numbers are missing on a hard 9x9 puzzle?
Around 55 of the 81 cells, leaving roughly 26 givens. The exact count varies slightly because any removal that would break the single-solution rule is put back.
Why is the 6x6 grid split into 2x3 boxes instead of squares?
Six cannot be made from two equal factors, so the boxes have to be rectangular for six of them to fill the board. Rows and columns still hold 1 to 6 exactly once, and so does each 2x3 box.
Do I need an account or will there be a watermark across the page?
No account, no sign-up, and nothing across the grid. The printed sheet carries one small line of grey text at the very bottom noting it was made at atc21s.org.
Can I print a whole page of puzzles at once?
Not in one click. Each print produces a single puzzle on its own sheet, sized to be comfortable to write in. For a batch, generate and print one after another, or download them as images and place several into a document yourself.
Is sudoku actually a maths exercise?
Not in the arithmetic sense, since nothing is added or multiplied. It is logical deduction practice using numbers as labels, which is why it suits children who are still shaky on their number facts but enjoy a puzzle.