Killer Sudoku

Printable Killer Sudoku Puzzles with Cage Sums

Killer Sudoku is the Sudoku variant that trades starting digits for cage clues. Instead of seeing numbers dotted around the grid, you see dashed outlines grouping cells into cages, each marked with a small sum. Your job is to place digits 1 to 9 so all the usual Sudoku rules hold and every cage’s cells add up to the listed sum without repeating a digit inside the cage.

This generator produces print-ready Killer Sudoku puzzles in A4 or US Letter PDF format, with one or two puzzles per page so the cage outlines and sums stay clearly visible. An optional solution page is available. Killer Sudoku is a rich form of brain training for solvers who already enjoy classic Sudoku and want to add an arithmetic layer.

Pattern recognition, deductive reasoning and number-bond fluency all come into play. Killer Sudoku makes a great quiet-time activity, travel puzzle and evening challenge for adults and older children with a solid grasp of addition.

How the Killer Sudoku rules work

Every standard Sudoku rule still applies: rows, columns and 3x3 boxes each contain the digits 1 to 9 exactly once. Cages add two extra rules.

• Each cage has a small printed sum in its top-left cell.
• The digits placed inside a cage must add up exactly to the cage sum.
• A digit may not repeat within a cage, even if the cage spans more than one row or box.
• Typically there are no starting digits; the cage sums provide all the information.

The combination of Sudoku logic and sum logic is what makes Killer Sudoku so satisfying.

Who Killer Sudoku is for

Beginners

If you already solve easy or medium classic Sudoku, Killer Sudoku is the natural next step. Start with cages made up of two or three cells and known magic sums.

Puzzle enthusiasts

Experienced solvers love Killer Sudoku for its elegant constraint weaving. Innie and outie techniques on cages and boxes form a whole vocabulary of deduction.

Classroom teachers

Killer Sudoku is arithmetic practice dressed up as a brain teaser. Pupils meet number bonds repeatedly while also exercising deductive reasoning.

Parents

Print a Killer Sudoku for a quiet afternoon or a long journey. The mix of logic and light arithmetic keeps it engaging for older children and adults alike.

What you can customise

• Puzzle count: one or two per page for clear cage outlines.
• Include solutions: add a second page with completed grids.
• Seed: lock the set by entering a fixed seed.
• Paper size: A4 or US Letter PDF output.

Worked example

Consider a two-cell cage labelled 3. The only way to make 3 from two distinct digits in 1 to 9 is 1+2. Now imagine a three-cell cage in the same row labelled 6. The possible triples of distinct digits from 1 to 9 summing to 6 are {1, 2, 3}. Because the first cage already takes a 1 and a 2 from the row, the three-cell cage cannot contain a 1 or a 2, which immediately rules out {1, 2, 3}. That contradiction proves the two cages cannot share a row layout as stated. In real puzzles you use these short contradictions to place digits step by step.

Magic sums shortcut many deductions. A two-cell cage of 17 must be {8, 9}, and a four-cell cage of 10 must be {1, 2, 3, 4}.

How to use the tool

1. Choose one or two puzzles per page.
2. Decide whether to include the solutions page.
3. Optionally set a seed for a repeatable set.
4. Select A4 or US Letter paper.
5. Click Generate and preview the puzzles.
6. Download the PDF and print at 100% scale.

Methodology

The generator first builds a fully solved Sudoku grid. It then groups cells into cages of one to four cells, chosen so cage members never repeat a digit. Each cage’s sum is computed from the hidden solution and printed as the clue. In v1 the engine derives cages from a real solved grid so a valid solution always exists, though strict uniqueness is not enforced. The printed solution page shows one valid completion.

Tips for solving

• Learn the common magic sums for two- and three-cell cages. They often pin down a cage immediately.
• Apply the “45 rule” per row, column and box. Each sums to 45, so the cage totals plus any dangling cells must also sum to 45.
• Look for innies and outies. A single cell that sits outside all cages within a box can be computed by subtracting from 45.
• Use pencil candidates to track which digits remain legal in each cage cell.

Designed for A4 and US Letter printing

Every PDF is laid out for both A4 and US Letter without scaling. One or two Killer Sudoku puzzles per page keeps the cage outlines and sum labels crisp even on basic printers.

Related logic puzzles

• Arrow Sudoku
• Diagonal Sudoku
• Irregular Sudoku
• Sudoku Generator
• Binary Puzzle Generator
• Number Pyramid Generator