What is killer sudoku?
Killer sudoku mixes classic sudoku with a touch of arithmetic. Instead of given numbers, the grid is divided into cages outlined with dotted lines, and each cage shows the sum of its digits. You still place 1 to 9 in every row, column and box, but now the sums guide every move.
It is the natural next step once regular sudoku feels easy. Play killer sudoku online free here, with a new puzzle whenever you want one.
How to play Killer Sudoku
- Every row, column and 3×3 box holds the digits 1 to 9 exactly once, as in normal sudoku.
- The grid is split into dotted cages, each with a small number in its corner.
- The digits in a cage must add up to that number.
- A digit can never repeat inside the same cage.
Killer Sudoku tips
Learn the unique cages
Some sums can only be made one way. A two-cell cage of 3 is always 1 and 2; a two-cell 17 is always 8 and 9; a three-cell 6 is always 1, 2 and 3.
Use the 45 rule
Every row, column and box adds up to 45. Add the cages that fit inside one box, subtract from 45, and you know the total of the cells left over, often a single cell.
Combine sums with normal sudoku
Once a cage is narrowed to a few digits, switch to ordinary scanning. Cage limits and sudoku rules together clear candidates fast.
Frequently asked questions
Do killer sudoku puzzles have starting numbers?
Usually not. Most killer sudoku grids start completely empty, and the cage sums are your only clues.
Is killer sudoku harder than normal sudoku?
It asks for a little arithmetic, but the easy levels are gentle. Many players find it more satisfying, because every cage gives you something to work with.
What is the 45 rule in killer sudoku?
Each row, column and 3×3 box contains 1 to 9, which always adds up to 45. Comparing that total with the cages lets you work out hidden sums.
