Killer Sudoku Rules — Complete Beginner's Guide
Killer Sudoku adds dotted-line 'cages' to a normal Sudoku grid. Each cage has a small target sum, and digits inside a cage may never repeat. Beyond that, every rule of classic Sudoku still applies.
The three rules
1) Standard Sudoku: fill every row, column and 3×3 box with digits 1–9 exactly once. 2) The digits inside a cage must add to the cage sum shown in its corner. 3) No digit may repeat inside a single cage.
Starter strategy: the 45 rule
Every row, column and box sums to 45. If a cage exactly covers a row, column or box, the leftover cells must sum to (45 − cage sum). This single insight breaks open most beginner puzzles.
Cage combinations to memorise
2-cell cage summing to 3 must be {1,2}. 3-cell summing to 6 must be {1,2,3}. 4-cell summing to 10 must be {1,2,3,4}. Mark these immediately.
Frequently asked
Do cages overlap?
No. Every cell belongs to exactly one cage and cages never share a cell.
Can I solve Killer Sudoku without arithmetic?
You'll do small sums, but most progress still comes from elimination, not addition.