Hard Killer Sudoku
Free printable hard killer sudoku puzzles for experienced solvers — very few given digits, cage sums do the work. One guaranteed solution. Play online, print, or download the puzzle and answer key as a PDF.
Fill the grid so 1–9 appears once in every row, column and 3×3 box. The digits in each dashed cage must add up to the small number in its corner, with no repeated digit inside a cage.
Click a cell, then pick a number.
Explore the The Sudoku Family & Grid Variations
Explore the full range of Sudoku variations — from classic 9×9 grids to diagonal constraints, cage sums, irregular polyominoes, and word-based puzzles.
Killer Sudoku
Arithmetic cage sums meet pure Latin square logic
Learn How to Play, Solve & Teach Hard Killer Sudoku
What Is Killer Sudoku? How to Solve It (Beginner's Guide)
Learn what killer sudoku is and how to solve it — the cage rules, the '45' trick, and simple cage-sum combinations. Play free online or print puzzles with the answer key.
Frequently asked questions
Is the killer sudoku generator free?+
Yes. Generate unlimited killer sudoku puzzles and play, print or download them for free — no account or signup needed.
How is killer sudoku different from regular sudoku?+
It follows all normal sudoku rules — 1 to 9 once per row, column and 3×3 box — plus dashed 'cages'. The digits in each cage must add up to the small number shown in its corner, and no digit repeats within a cage.
Do the cages start with given numbers?+
Killer sudoku uses far fewer given digits than regular sudoku — the cage sums do most of the work. Easy puzzles include more starting clues; hard puzzles have very few.
Does every puzzle have one solution?+
Yes. We remove clues only while a solver confirms the puzzle still has exactly one unique solution, so every killer sudoku is solvable by logic alone.
How do I print a killer sudoku?+
Click Preview & Download, choose US Letter or A4, and download the PDF. It includes the puzzle with the cage sums plus a separate answer key page.