Printable sudoku puzzles
Free printable sudoku puzzles
Every grid has exactly one solution and never needs a guess. Print a set, or build one at any difficulty. 32 to print, or build your own.
- Easy sudoku 12 puzzles. Around 40 given numbers, so every step follows from what is already on the grid. Right for a first sudoku, or a quiet ten minutes.
- Medium sudoku 12 puzzles. Fewer givens, and some cells need you to look at a row, a column and a box together before the answer appears.
- Hard sudoku 8 puzzles. Around 26 givens. Every puzzle still has exactly one solution and never needs a guess, but finding the next move takes real attention.
How these grids are made
Each puzzle starts from a complete, valid solution built by randomised backtracking: the solver fills squares in a shuffled order and reverses whenever it paints itself into a corner. Numbers are then dug out one at a time, and after every removal the grid is re-solved to confirm it still has exactly one answer. A square whose removal would allow two solutions goes back in.
That check is the whole difference between a sudoku and a grid of numbers. A puzzle with two solutions cannot be reasoned to an answer, only guessed at, and a solver who has spent twenty minutes on one has been cheated rather than challenged. It also means the printed answer key is the answer rather than an answer.
Reading a grid for the first time
Scan rather than stare. Pick a number, look at the three boxes in a band, and ask where it can still go in each: often two of the three boxes already hold it, and the third has only one square left open. That single technique, called cross-hatching, finishes most easy grids on its own.
When scanning stops paying, switch to the square rather than the number. Take an empty cell, list what its row, column and box have not used, and write those candidates small in the corner. A cell with one candidate is an answer. A number that appears as a candidate in only one cell of a box is also an answer, even where that cell has several candidates, which is the step most people miss.
Difficulty here is a measure of which techniques a grid forces, not simply how many numbers it withholds. Easy sets fall to cross-hatching. Medium sets need candidates written down. Hard sets need you to reason about pairs: two cells in a unit that share the same two candidates lock those numbers between them, which clears both from every other cell around.
Questions about printable sudokus
- Where can I find free printable sudoku puzzles?
- Each difficulty here is a printable set rather than a single grid, with the answers on the page. Print the whole set or download one puzzle as a PDF. There is no account and no limit on copies.
- What is the 45 rule in sudoku?
- Every row, column and box contains one to nine exactly once, so each adds up to 45. That lets you find a single missing number without checking candidates: total what is already in the unit and subtract from 45. It is most useful on killer sudoku, where cages give you sums to work with.
- Does every sudoku here have one solution?
- Yes. Numbers are dug out of a completed grid one at a time and the puzzle is re-solved after each removal to confirm the answer is still unique. A square whose removal would allow two solutions goes back in. A grid with two answers cannot be reasoned out, only guessed at.
- Can I play sudoku online free without ads on the grid?
- You can play every sudoku here in the browser with no sign-up, and your grid and timer are kept if you close the tab. Pencil marks and undo are built in. Nothing is placed over the board itself.