How to play Killer Sudoku?

Play Killer Sudoku by following the normal Sudoku rule in every row, column, and 3x3 box, while also making the digits inside each outlined cage add up to its printed total. In standard Killer Sudoku, a digit cannot repeat within a cage.

Start with constrained cage totals

Look first for cages with very few possible combinations. A two-cell cage totaling 3 must contain 1 and 2; a two-cell cage totaling 17 must contain 8 and 9. Row, column, and box restrictions determine which cell gets which digit.

• Write possible combinations beside each cage before assigning them to cells.
• Remove a combination as soon as one of its digits conflicts with the row, column, or box.
• Use the 45 rule: every complete row, column, and 3x3 box totals 45.
• When a set of cages almost fills a unit, subtract their totals from 45 to find the missing cells.

How it differs from classic Sudoku

Many Killer Sudoku puzzles begin with few or no placed digits, so cage arithmetic supplies the opening clues. SudokuPrintable.com currently generates classic Sudoku rather than Killer Sudoku, but the blank Sudoku grid is useful for copying a Killer puzzle and the standard rules still apply outside the cages.