sudokly
129
9×9 · Medium to evil

Killer Sudoku

Sudoku meets killer-style arithmetic: every dotted region sums to its total.

Killer·00:00
About killer

What killer sudoku feels like.

Killer sudoku layers an arithmetic constraint on top of classic sudoku. Cells are grouped into dotted cages, and each cage's cells must sum to the small total printed in its corner. As in classic sudoku, no digit repeats in a row, column, or 3×3 box. and no digit repeats inside a cage either.

Rules

  1. Standard sudoku rules apply: each digit 1–9 appears exactly once per row, column, and 3×3 box.
  2. Cells are grouped into cages outlined by dotted borders.
  3. Each cage shows a target sum in its top-left corner.
  4. Cells in a cage must sum to that target, and no digit repeats inside a cage.

History

Killer sudoku appeared in Japan in the 1990s and was popularised in the UK by The Times in 2005. It bridges sudoku and the older Japanese puzzle Kakuro.

Key rule
Cages with sum totals; no repeats in cages
Difficulty range
Medium to evil
Tips
  • Start with the smallest cages. A 2-cell cage summing to 3 must be {1, 2}.
  • Look for cages that sum to extremes. small (3, 4) or large (16, 17). they have only one digit combination.
  • The full row, column, or box sums to 45. If you know all but one cage, you know what's left.
  • Treat each cage as a sudoku-within-sudoku for candidate elimination.

Killer Sudoku FAQ

What is killer sudoku?

Killer sudoku is a sudoku variant where the grid contains no starting clues. Instead, cells are grouped into outlined cages, each with a target sum. Cells in a cage must sum to the target without repeating any digit.

Is killer sudoku harder than regular sudoku?

Generally yes. Killer sudoku usually starts with no given numbers, so you derive everything from cage sums. Easy killer is roughly equivalent to medium classic.

Can killer sudoku be solved with logic?

Yes. Every well-formed killer sudoku has exactly one solution reachable with logic. no guessing required.

What's the smallest possible cage?

A single cell. Single-cell cages are essentially given clues. the target sum is the digit.

Do digits repeat inside a cage?

No. Even though arithmetic might allow it (4+4=8), killer rules forbid repetition inside a cage.