Killer sudoku
Sudoku with sums: three levels and a daily puzzle
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How to play, in one minute
Killer sudoku is sudoku with an extra rule. Every row, column and 3 by 3 box still needs 1 to 9 once each, but the grid is also split into cages with dashed outlines, and the numbers in a cage have to add up to the small number in its corner. A number can't repeat inside a cage.
- Pick a square, tap a number. The cage you picked lights up, and the line under the board lists every set of numbers that can make its sum. Turn that off in Settings if you'd rather work it out.
- Start with the easy cages. A cage of 2 squares adding up to 3 can only be 1 and 2. A cage of 3 adding up to 24 can only be 7, 8 and 9. Those are your first footholds.
- Use the rule of 45. Each row, column and box adds up to 45. If the cages inside a row add up to 38 and one square is left over, that square is 7.
- Mistakes turn the square red and say why, for example "There's already a 6 in this cage." Three mistakes and the puzzle starts over (you can switch that off in Settings).
The full rules, a worked example and a printable cheat sheet with every cage combination are on our killer sudoku rules and combinations page.
What the levels mean
Every puzzle here has exactly one solution, and our solver finished each one using moves a person can make, without guessing. The levels differ in cage size and in which moves you need:
| Level | Numbers given | Cage sizes | What it takes |
|---|---|---|---|
| Easy | 3 to 9 | 2 or 3 squares | Cage combinations and singles only |
| Medium | None | 2 to 4 squares | Also the rule of 45 on 1 to 3 squares |
| Hard | None | 2 to 5 squares | Bigger cages, and some need the rule of 45 on 4 or more squares |
Measured on our puzzle banks (150 easy, 200 medium and 150 hard puzzles), October 2026. All 200 medium puzzles needed the rule of 45 at least once. 136 of the 150 hard puzzles have a 5-square cage, and 56 needed a move that no medium puzzle needs. An average cage has 2.4 squares on easy, 2.6 on medium and 2.9 on hard.
Questions
Is it free?
Yes. No account, no download and no limit on puzzles. The site may show ads in the future to pay for itself; they'll never cover the board.
How is killer sudoku different from regular sudoku?
Regular sudoku starts with numbers filled in. Killer sudoku usually starts empty and gives you sums instead: each dashed cage tells you what its numbers add up to. So you mix sudoku logic with a little adding. Our easy level gives you 3 to 9 starting numbers to get going; medium and hard give none.
Can a number repeat inside a cage?
No. A cage of 2 squares adding up to 4 has to be 1 and 3, never 2 and 2. That rule is what makes small cages so useful.
What's the rule of 45?
The numbers 1 to 9 add up to 45, so every row, every column and every box does too. Add up the cages that sit fully inside one row, take that from 45, and you know what the leftover squares add up to. Our how to play killer sudoku page has a worked example.
Is there a daily killer sudoku?
Yes, a new medium puzzle every day at daily killer sudoku. Everyone gets the same one, and solving it adds to your daily streak.
Will I lose my game if I close the page?
No. Your puzzle, notes and time are saved in this browser after every move, one game per level. Clearing your browser data or switching devices starts fresh.
How do hints work?
Hint fills in the square you picked, or the next square a person could work out, and says why: a cage combination, the rule of 45, or a single. You get 6 hints per puzzle.
More sudoku
- Daily sudokuA new easy, medium and hard puzzle every day, the same for everyone.
- Easy sudokuPlenty of clues. Every move can be found by looking for single options.
- Medium sudokuFewer clues, same simple logic. A good daily level.
- Hard sudokuNeeds pairs and pointing pairs, not just singles.
- Expert sudokuNeeds X-wings or triples. Still no guessing.
- Daily killer sudokuOne new killer sudoku every day, with its own streak.
- Killer sudoku rules and combinationsThe rule of 45, a worked example and every cage combination.
- Printable sudokuLarge-print sheets for pencil and paper, with answers.
- How to play sudokuThe rules, a first walk-through and the controls on this site.
- Sudoku strategiesFrom hidden singles to X-wings, with examples.