Killer Sudoku – Expert
Killer Sudoku hands you an almost empty grid. Instead of given digits you get cages: dotted regions with a small total in the corner. The digits inside a cage must add up to that total and must all be different.
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Building a puzzle with a single solution…
The rules in three lines
- Normal Sudoku rules apply: every row, column and box holds the digits 1 to 9 exactly once.
- The digits in a dotted cage add up to the number printed in its corner.
- No digit repeats inside a cage — a cage of two summing to 10 can be 1+9 or 2+8, never 5+5.
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Frequently asked questions
- What is Killer Sudoku?
- Killer Sudoku combines Sudoku with simple addition. The grid starts almost empty; instead of given digits you get dotted cages, each labelled with the total its digits must reach. Normal Sudoku rules still apply on top of that.
- Can a digit repeat inside a cage?
- No. Every digit inside one cage must be different, which is what makes the sums informative. A two-cell cage totalling 10 can be 1+9, 2+8, 3+7 or 4+6 — never 5+5.
- How do I start a Killer Sudoku?
- Look for the extreme sums first. A two-cell cage of 3 can only be 1+2, a three-cell cage of 6 only 1+2+3, and a four-cell cage of 30 only 6+7+8+9. Those forced cages give you the first real footholds.
- What is the rule of 45?
- Every row, column and box contains 1 to 9 exactly once, so its digits always add up to 45. If the cages inside a box account for 40, the remaining cell must be 5. This single observation solves a surprising number of positions.
- Is Killer Sudoku harder than normal Sudoku?
- At first it feels harder because nothing is given. In practice the cage sums carry more information than a handful of starting digits, so once you know the standard combinations an easy Killer plays much like an easy classic puzzle.