Killer Sudoku
Sum cages & smarter challenges
9×9 grid with sum cages · arithmetic meets logic
Goal
Solve a Sudoku where dotted “cages” must each add up to a printed total, with no digit repeated inside a cage.
Rules
- All normal Sudoku rules apply: 1–9 once per row, column, and box.
- Each dotted cage must sum to its small printed total.
- A digit cannot repeat within a single cage.
- There are usually no given digits — the cage sums are your way in.
How to play
- Find cages with only one combination (a 2-cell cage summing to 3 must be 1 and 2).
- Use the Rule of 45: each row, column, and box totals 45, so leftover cells are forced.
- Blend cage arithmetic with ordinary Sudoku scanning.
Tip
Memorise the unique sums — two cells totalling 3 is {1,2}; totalling 17 is {8,9}.
Techniques to learn
Naked Single · Hidden Single · Last Candidate · Cage Remainder · Naked Pair · Hidden Pair · Pointing Pair · Box-Line Reduction · Naked Triple · Hidden Triple · Cage Combination · Rule of 45 · X-Wing · Y-Wing · XYZ-Wing · Skyscraper · Two-String Kite · Empty Rectangle · Naked Quad · Hidden Quad · W-Wing · Swordfish · Jellyfish · Finned Fish · Simple Coloring · X-Chain · XY-Chain · Inference Chain · ALS-XZ