Killer Sudoku

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What Is Killer Sudoku?

Killer sudoku is sudoku's arithmetic-heavy cousin. The grid obeys all the classic placement rules, but almost no numbers are given at the start. Instead the grid is divided into dotted cages — small clusters of cells, each printed with a target sum. The numbers inside every cage must add up to that target. The result is a puzzle that forces you to blend sudoku logic with mental arithmetic from the very first move.

The game on this page is our take on the same idea: sudoku-style rows and columns plus arithmetic cages. It strips out the 3×3 boxes so puzzles stay phone-friendly, and it adds multiplication and division cages on top of the usual sums.

Killer Sudoku Rules: Cages and the 1–9 Rule

Fill the grid with 1–9. Every row and every column must contain each digit exactly once (classic killer sudoku adds the 3×3 box rule; this version replaces it with cage arithmetic for a lighter mental load).
Each cage has a printed target. The numbers in that cage must reach it with the cage's operation: + for sums, and in this version also −, × and ÷ for two-cell cages.
The 1–9 rule: in classic killer sudoku, digits never repeat inside a cage. A 2-cell cage totalling 17 can only be 8 + 9 — knowing that fact alone cracks half the puzzle.
A cage showing a single number is already filled in — use those givens as anchors.

Killer Sudoku vs Sudoku: What's the Difference?

Classic sudoku hands you a scatter of given digits and is pure placement logic — no arithmetic at all. Killer sudoku removes most of those givens and replaces them with cage sums, so you deduce which digits go together before you deduce where they go. The cage arithmetic is a tool, not an obstacle: a cage totalling 3 in two cells can only be {1, 2}, and every such deduction narrows the grid. This puzzle sits between the two — cage logic like killer sudoku, but with a smaller grid and four operations, so a full puzzle takes minutes rather than an hour.

Killer Sudoku Tips and Solving Strategies

Memorise the small combinations. Two-cell cages: 3 = 1+2, 4 = 1+3, 16 = 7+9, 17 = 8+9. Three-cell: 6 = 1+2+3, 7 = 1+2+4, 24 = 7+8+9. These forced sets are your starting moves.
Chase the extreme cages. Very small or very large targets have the fewest possible digit sets, so open there and cross-reference with rows and columns.
Use the 45 rule on boxes. In a real killer sudoku, each 3×3 box sums to 45 — cages that stick out of a box by one or two cells give you those cells' values directly.
Watch division and subtraction cages: a ÷ cage with target 2 hides {1,2}, {2,4} or {3,6} — the row and column decide which.

Play Free Killer Sudoku Online

The grid above is free to play right now — no download, no sign-up. The daily puzzle refreshes at midnight UTC and is the same for everyone, with difficulty rotating through the week; practice mode gives unlimited grids at your chosen size. Solve fast without hints for ★★★, and share your time when the cages finally click.