Expert Killer Sudoku
Cage sums meet classic Sudoku logic. Digits in each cage must total the clue — no repeats allowed. Free, no login required.
Expert Killer Sudoku. Zero given digits, rare cage combinations, and interactions that span the entire grid. Every placement follows from precise logic. No guessing.
How to play Killer Sudoku
Killer Sudoku - Complete Guide
Forced cage combinations you must memorise
Key solving techniques
Every row, column, and 3x3 box sums to 45. If all cages in a row are known except one cell, the missing value = 45 - (sum of all other cage totals in that row). This is the single most powerful Killer technique.
When a cage partially straddles a row/column/box boundary, the cells inside the boundary are "innies" and those outside are "outies." Their sum difference reveals exact values using the 45 rule, often resolving cells without any candidates.
When a cage spans two boxes or rows, use subset counting to pin down which digits appear in the overlap region. Subtract partial cage sums to isolate individual cell values - Especially useful when the 45 rule leaves two unknowns.
If a group of cages within a unit accounts for exactly n cells using n digits, those digits are locked to those cells and removed from all other unit cells. Identical to classic naked pairs/triples but applied across cage boundaries.
Frequently Asked Questions
What is Killer Sudoku?
Solving Techniques for Expert Level
| Technique | Description | Level |
|---|---|---|
| Cage Sum Elimination | Each cage has a fixed sum. Use the sum and the number of cells to calculate which digits are possible — e.g. a 2-cell cage summing to 3 can only be {1,2}. | Beginner |
| No-Repeat Rule | Digits cannot repeat within a cage. Combined with sum constraints, this eliminates many candidates immediately. | Beginner |
| 45 Rule | Each row, column, and box sums to 45. Subtract known cage totals within a unit to find leftover cell sums — often isolating a single value. | Intermediate |
| Innies and Outies | An innie is a cage cell inside a unit whose sum reveals a digit; an outie is outside. These provide single-cell deductions without full candidate tracking. | Intermediate |
| Cage Overlap Counting | When a cage spans two boxes or rows, use subset counting to pin down which digits appear in the overlap cells. | Advanced |
| Naked Subset in Cages | If a group of cages within a unit accounts for exactly n cells using n digits, those digits are locked to those cells and removed from all other unit cells. | Advanced |
Techniques to Master at Expert
- X-Wing technique — Expert killers withhold single-combination cages, so opening progress is slow — alternate 45-rule sweeps with X-Wing scans, as each elimination re-prices every cage it touches.
- Swordfish technique — Once cage logic confines a digit to matching columns across three rows, the Swordfish elimination feeds straight back into the cage sums — the expert killer's closing argument.
Average Solve Time by Difficulty
Related Variants
Keeps the sum-clue arithmetic but moves it onto diagonals where digits may repeat — a deliberate twist on your cage instincts.
Another sum-driven puzzle: instead of cage totals you deduce which digits sit between the 1 and the 9 in each row and column.
Swaps cages for arrows whose shaft must add up to the circled digit — the same combination-counting muscle in a linear shape.
Frequently Asked Questions — Expert Killer Sudoku
More questions? See the full Killer Sudoku FAQ.