Killer Sudoku.
Learn the rules, see the possibilities.
Killer Sudoku combines the familiar row, column, and box rules with small groups of cells called cages. Each cage has a target sum. Its entries must add up to that total without repeating a digit inside the cage. Use both placement logic and simple addition to narrow the possibilities.
How to play Killer Sudoku
Three ideas. Illustrated on the board. Take them one move at a time.
Read the small number in a cage
A dashed outline marks the cells that belong to one cage. The small number in its first cell is the target total, not an entry for that cell. In this example, two cells add up to 3, so they must contain 1 and 2. Their order still depends on the rest of the board.
A cage can cross a box boundary. Follow its outline rather than the thicker box lines.
Find combinations before positions
For a two-cell cage totaling 10, the possible unordered pairs are 1 and 9, 2 and 8, 3 and 7, or 4 and 6. The pair 5 and 5 is not allowed because a digit cannot repeat in a cage. Check the crossing rows and columns to decide which pair can actually fit.
Keep the possible combinations separate from the question of which cell gets which digit.
Connect cages with the Sudoku rules
A correct sum alone is not enough. Every cage entry must also fit its row, column, and box. On a 9×9 board, any complete row, column, or box totals 45. When cages cover most of one of these groups, subtracting their sums can sometimes reveal what remains.
Use the 45 total only for a complete 1–9 unit. A partial cage may extend outside that unit.
Sudoku strategies that work in every variant
Every Sudoku is solved with the same three habits. They need no arithmetic and no guessing — just a careful look at what each cell can still be.
Scan rows, columns, and boxes
Pick a number and sweep the grid. Where a number already appears, it cannot go again in that row, column, or box. Three placed copies often leave only one open cell for the fourth.
Hunt for singles
Look for a cell with just one possible symbol left. A row or box that is almost complete is the fastest place to find one, and each single you place narrows the next cell.
Write candidates, then eliminate
When two or three cells stay open, switch on Notes and pencil in the possibilities. Cross out candidates as peers fill in. If a digit fits only one cell inside a group, that cell must hold it.
A few Killer Sudoku facts
The 1–9 total
Useful when cages partition a complete row, column, or box.
Smallest two-cell sum
With distinct positive digits, the pair is 1 and 2.
Largest two-cell sum
On a 9×9 board, the pair must be 8 and 9.
These examples and figures describe a standard 9×9 board unless otherwise stated.
Make yourself at home on the board.
Choose a cell, enter a symbol, and keep going. Use Notes for possibilities, Undo to revisit a move, and Hint when you need a nudge. Change the visual theme without changing your game.
- ↑↓←→
- Move between cells
- 1–9
- Enter a number; use the keypad for larger symbol sets
- Del
- Erase your entry
- Ctrl / ⌘Z
- Undo the last move
Killer Sudoku, explained.
A few things you might be wondering.
Can a digit repeat inside a Killer Sudoku cage?
No. Even if repeating a digit would produce the right sum, the digits in a single cage must be distinct. Row, column, and box rules still apply.
Does the cage sum count as a number in the grid?
No. The small cage total is a clue for the whole outlined group. You still enter one regular digit in each of its cells.
Why does this Killer Sudoku include given digits?
Sudokuzz uses cages together with fixed starting digits. These clues help you learn the variant while the cage-sum and no-repeat rules remain in effect.