Killer Sudoku: Rules and How to Play (Beginner's Guide)
Quick answer: Killer Sudoku is classic Sudoku plus simple addition. The grid is split into dashed cages, each labelled with a target sum; the cells in a cage must add up to that number without repeating a digit — on top of the usual rule that every row, column, and 3x3 box holds 1 to 9 once. There are no starting numbers, so the cage sums are your clues.
If you have mastered classic Sudoku, Killer Sudoku is the most popular next step. Here is how it works.
The rules of Killer Sudoku
Killer keeps every classic Sudoku rule and adds one layer:
- Rows, columns, and boxes: each must contain 1 to 9 exactly once — same as always.
- Cages: the grid is divided into dashed-outline groups of cells. The small number in a cage’s corner is the sum its cells must add up to.
- No repeats in a cage: a digit cannot appear twice inside the same cage (even if the box rule would otherwise allow it).
Crucially, a Killer puzzle usually starts empty — no given digits. The cage sums are the only clues, and that is enough.
Start with the small cages
Low-cell cages with extreme sums have very few combinations, so they are the best foothold:
- A 2-cell cage summing to 3 can only be 1 + 2.
- A 2-cell cage summing to 17 can only be 8 + 9.
- A 3-cell cage summing to 6 can only be 1 + 2 + 3.
You may not know the order yet, but you have narrowed those cells to two or three candidates — exactly like a naked pair in classic Sudoku.
Use the 45 rule to break in
Every row, column, and 3x3 box adds up to 45 (1+2+…+9). This is Killer’s signature trick:
If cages neatly fill a row, column, or box except for one stray cell, add up those cage sums and subtract from 45. The remainder is that cell’s value.
The same idea works when a cage pokes just one cell out of a box — the “innie” or “outie” — letting you pin down a single number.
Then it plays like Sudoku
Once cage logic gives you a few placements and candidate pairs, the puzzle solves with the same techniques as classic Sudoku — hidden singles, naked pairs, pointing groups. The cages simply hand you a head start that a normal grid never would.
Ready to try one? Killer Sudoku is a built-in mode in the Sudoku Aura app. For the full family of variants, see our guide to the types of Sudoku, or play a free classic puzzle to warm up.
