About Killer Sudoku
Killer Sudoku combines Sudoku with the arithmetic of Kakuro. There are few or no starting digits; instead, dashed cages show the sum of the digits inside them. Every puzzle here has exactly one solution that can be found by logic, so you never need to guess.
How to play
Fill the grid so every row, column and 3×3 box contains 1–9 exactly once. Dashed cages group cells: the digits in a cage must add up to the small number in its corner, and no digit repeats within a cage. Use notes to track candidates.
Tips and strategies
- Learn the unique sums: a 2-cell cage of 3 is always 1+2, and 17 is always 8+9.
- Use the 45 rule: every row, column and box adds up to 45, so you can calculate cells that stick out of the cages inside it.
- A cage never repeats a digit, even when its cells lie in different boxes.
Killer Sudoku strategy guide
Learn the fixed cages. Two cells adding to 3 can only be 1+2, to 4 only 1+3, to 16 only 7+9 and to 17 only 8+9; three cells adding to 6 must be 1+2+3 and to 24 must be 7+8+9. These cages give you digits straight away.
Use the 45 rule. Every row, column and box adds up to 45. Add up the cages that lie entirely inside a box; the difference from 45 is the sum of the cells left over, often a single cell you can fill at once.
Combine sums with ordinary Sudoku logic. Once a cage's possible digit sets are narrowed down, hidden singles, pairs and pointing finish the job. For bigger cages, note the possible combinations rather than single digits.
Frequently asked questions
How is Killer Sudoku different from Sudoku?
The grid follows the same rules, 1 to 9 in every row, column and box, but it starts with few or no digits. Instead, dashed cages show the sum of their cells, and a digit can't repeat inside a cage.
What changes between the difficulties?
Cage sizes and starting digits: Easy has cages of 2–3 cells and 18 digits filled in, Medium 2–4 cells and 6 digits, Hard 2–5 cells on an empty grid, and Expert 3–6 cells on an empty grid.
Does every Killer Sudoku have exactly one solution?
Yes. A cage-aware solver checks each puzzle before you play, so there is exactly one solution and logic is enough to find it.
Is Killer Sudoku free to play?
Yes. Every game on Puzzimo is completely free and runs in your browser on desktop, tablet and phone — no download or installation.
Do I need an account?
No. You can play instantly as a guest and still appear on the leaderboards. Sign in with Google, Discord or LINE to keep your scores on every device.
How does the daily Killer Sudoku challenge work?
Every day at 00:00 UTC everyone gets the same new puzzle. Only your first finish of the day counts on the leaderboard.
How are leaderboard results verified?
Our servers replay every move of your game and measure the time themselves, so leaderboard results can't be faked.