easy
Small cages and direct sums. No guessing required.
0 of 25 free easy Killer Sudoku puzzles used
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Killer Sudoku
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medium
Cage arithmetic plus row, column and box pressure. Still no guessing.
0 of 25 free medium Killer Sudoku puzzles used
hard
Tighter cage interactions and rule-of-45 chains. Branching guesses may be required.
0 of 25 free hard Killer Sudoku puzzles used
From the rulebook
How to play Killer Sudoku
Killer Sudoku (also called sum Sudoku) follows all the classic Sudoku rules, digits 1–9 once per row, column and 3×3 box, but the grid starts with no given digits. Instead, the board is divided into dotted cages, and the digits in each cage must add up to the cage's printed total without repeating a digit.
Start with the extreme cages: a two-cell cage totalling 3 can only be 1+2, and one totalling 17 can only be 8+9. The “rule of 45” is the key technique, every row, column and box sums to 45, so comparing cage totals against 45 reveals single cells. Combine cage arithmetic with ordinary Sudoku eliminations to crack the harder grids.