How to play
Killer Sudoku rules
Killer Sudoku combines Sudoku with addition. Every standard Sudoku rule still applies — plus a few new ones for the cages.
- Fill 1–9 in every row
Each of the nine rows must contain the digits 1 to 9 exactly once.
- Fill 1–9 in every column
Each column must contain the digits 1 to 9 exactly once.
- Fill 1–9 in every 3×3 box
Each of the nine 3×3 boxes must contain the digits 1 to 9 exactly once.
- Cage sums must match
A cage is a group of cells outlined with a dashed border. The small number in the top-left of a cage is the total — the digits inside the cage must add up to exactly that number.
- No repeats inside a cage
A digit may not appear more than once in the same cage, even if it could otherwise be valid.
A useful fact
The digits 1 to 9 sum to 45. A solved Sudoku has nine rows each summing to 45, so the grand total is 405. Since cages cover every cell exactly once, the cage sums must total 405 too — a quick sanity check before you even start solving.