Killer Sudoku Game
cage sums · no operators · pure logic

How to play Killer Sudoku

Sudoku rules plus cages: the digits in each dotted cage add up to its total and never repeat.

The rules

  1. The grid is 9×9 with nine 3×3 boxes, and the usual Sudoku rules apply: each row, column and box holds 1–9 once.
  2. Dotted outlines called cages cover every cell. The small number in a cage's corner is its total.
  3. The digits in a cage must add up to the total.
  4. A digit cannot repeat inside a cage — even if the cage spans two boxes.
  5. Usually no digits are given at the start: everything comes from the cage totals.

Playing here

  1. Choose a grid size and a difficulty, then press Generate Puzzle.
  2. Click a cell and type a digit, or use the on-screen keypad. Notes switches to pencil marks.
  3. Undo steps back; Force places one digit that has only one possible value; Check marks mistakes in red without giving away the answer.
  4. Stuck? Send to Solver opens the same puzzle in the step-by-step solver. Send to Slate opens it as a board on the Slate whiteboard, to solve in front of a class.

Tips

The full guide, with a worked example and common mistakes: How to play Killer Sudoku.

Questions

Can a Killer Sudoku cage repeat a digit?

No. Unlike some arithmetic cage puzzles, digits never repeat inside a Killer Sudoku cage.

What is the 45 rule?

1+2+…+9 = 45, so every row, column and 3×3 box adds up to 45. Subtracting the cage totals you know from 45 reveals the sum of the cells that are left.

Where can I look up cage combinations?

Use the cage calculator, or the printable cage combinations table.

Is Killer Sudoku harder than Sudoku?

Usually, because there are no givens. But the cage totals add information, and easy Killer puzzles can be solved with combinations alone.

Can the solver explain each step?

Yes. Build the cages in the Killer Sudoku Solver and it explains every deduction — cage arithmetic, box logic, singles and pairs.

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