About Killer Sudoku
Play Killer Sudoku online for free. Solve a standard 9×9 Sudoku grid with an added twist: dashed-outline cages must sum to the small number printed in their corner, and no digit repeats within a cage. It rewards both Sudoku logic and quick arithmetic.
The Rules
Classic Sudoku rules, plus dashed cages that must sum to the number shown — no digit repeats within a cage.
Step by Step
- Standard Sudoku rules apply: 1–9 once per row, column, and 3×3 box.
- Cells inside a dashed cage must sum to the small clue number in that cage's corner.
- No digit can repeat within a single cage.
- Use cage sums to narrow down candidates before you have enough of the grid filled in for normal Sudoku logic.
Tips & Strategy
- Small cages (2 cells) with a low or high sum often have only one or two possible digit pairs.
- Look for cages that span exactly one row, column, or box — their sum tells you a lot about the missing digits.
- Combine cage-sum deduction with normal row/column/box elimination for the fastest progress.
- Two-cell cages that sum to 4 or 16 leave only one digit pair possible — memorize the extreme sums first, they pay off constantly.
Frequently Asked Questions
Do normal Sudoku rules still apply in Killer Sudoku?
Yes — every row, column, and 3×3 box still needs the digits 1–9 exactly once, on top of the cage sums.
Can a digit repeat inside a cage?
No. Every digit inside a single cage must be different, even if the cage spans multiple rows or boxes.
Is Killer Sudoku harder than regular Sudoku?
Generally yes for a given board size — cage arithmetic adds a layer of reasoning on top of the row/column/box rules, though it also gives you extra information to work with.
