Killer Sudoku — printable PDFs
Killer Sudoku adds arithmetic to the logic. The grid is divided into dashed-line cages, each labelled with a target sum in the top-left corner. The digits inside a cage must add up to that sum, with no digit repeating inside the cage. The standard 1–9 row, column, and box rules all still apply on top. Expert-tier Killer puzzles start with zero given digits — the cage sums alone uniquely constrain the solution.
Rules: standard Sudoku rules plus each dashed cage must sum to its target, with no repeated digits inside the cage. Start with small cages (2–3 cells) where the possible digit combinations are limited — a two-cell cage summing to 3 must be 1+2, a three-cell cage summing to 6 must be 1+2+3.
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Easy
Easy puzzles are solvable with plain row, column, and box scanning — no pencil-mark techniques required. A good choice for kids learning the rules, for warm-ups, or for a relaxed evening solve.
30 puzzles
Medium
Medium puzzles start to need basic pencil-mark techniques: naked pairs (two cells in a unit that can only be two specific digits) and hidden singles across wider units. A typical solve runs 7–15 minutes.
30 puzzles
Hard
Hard puzzles introduce locked candidates, pointing pairs, and box-row interactions. Expect 15–25 minutes per puzzle if you're comfortable with those techniques — and steady pencil-mark discipline.
30 puzzles
Expert
Expert puzzles lean on X-wings, coloring, and combined chain logic. Not a starting tier — but a natural step if you've been finishing Hard in ten minutes or less.
30 puzzles