Play Killer Sudoku Free Online

How to play Killer Sudoku (Sum Sudoku)

Killer Sudoku, also called sum Sudoku, combines Sudoku with arithmetic. The grid is divided into dotted cages, each showing a small target number. The digits in a cage must add up to that target and never repeat — on top of the normal Sudoku rules.

1. 1Follow Sudoku rules. Every row, column and 3×3 box must contain 1–9 with no repeats.
2. 2Make each cage sum correct. The digits inside each dotted cage must add up to the small number shown in its corner.
3. 3Never repeat inside a cage. A digit can't appear twice within the same cage, even if the sum would still work.
4. 4Use the rule of 45. Each row, column and box totals 45. Compare that to the cage sums crossing it to deduce missing digits.
5. 5Pencil in cage combinations. Use Notes to track which digit combinations can make each cage's sum, then eliminate as you solve.

Tips & strategy

Hunt for cages with few combinations: a 2-cell cage summing to 3 must be {1,2}; a 3-cell cage summing to 6 must be {1,2,3}. These 'locked' cages give you certain digits to anchor the rest of the grid. The rule of 45 across a box with one cage poking out is the classic next step.