Play Now
Killer Sudoku
Killer Sudoku is a hybrid of Sudoku and Kakuro that became popular in the early 2000s. The grid has no given digits; instead, dotted outlines mark "cages" of cells, each labeled with a small target sum. You combine standard Sudoku logic with arithmetic to crack it.
Killer Sudoku Rules
The board is a standard 9×9 Sudoku grid. Every row, every column, and each of the nine 3×3 boxes must contain the digits 1 through 9 exactly once. Unlike ordinary Sudoku, you begin with no filled-in numbers at all.
Cells are grouped into dashed-outline cages. The digits inside a cage must add up to the small number printed in its top-left corner, and no digit may repeat within a single cage — even if that cage spans more than one row or box.
You solve by combining the standard one-of-each rule with the cage sums. The puzzle is complete when the whole grid satisfies Sudoku's rules and every cage totals exactly its target, which yields one unique solution.
Killer Sudoku Strategy & Tips
Memorize small-cage combinations
Some sums force their digits. A two-cell cage of 3 must be 1+2; a 4 must be 1+3; a 16 must be 7+9. Two-cell 17 is 8+9. Locking these down early gives you anchor candidates.
Use the rule of 45
Every row, column, and box sums to 45. If cages neatly cover a region except for one stray cell, subtract the cage totals from 45 to find that cell's exact value.
Watch for overlapping cages and boxes
When several cages sit entirely inside one 3×3 box, the leftover cells must hold the missing digits. Add the cage sums and compare to 45 to pin down what remains.
Eliminate, don't guess
Treat each cage as a set of possible digit combinations, then cross off any that conflict with the row, column, or box. Pencil in candidates and remove them until a single value survives.
Frequently Asked Questions
What is the difference between Killer Sudoku and regular Sudoku?
Regular Sudoku gives you starting numbers; Killer Sudoku gives you none. Instead it provides cage sums, so you must use arithmetic alongside the usual one-of-each logic.
Can a digit repeat inside a Killer Sudoku cage?
No. A digit can never repeat within a single cage, in addition to the normal rule of no repeats in any row, column, or 3×3 box.
What is the rule of 45 in Killer Sudoku?
Because each row, column, and box holds 1 through 9, every one of them sums to 45. You can use that total to deduce missing cells when cages nearly fill a region.
Is Killer Sudoku harder than normal Sudoku?
Generally yes. With no given digits and the added arithmetic layer, even "easy" Killer puzzles demand more steps than a typical Sudoku of the same rating.