Killer Sudoku Combinations - Complete Cheat Sheet

The 45 Rule is the most powerful technique in Killer Sudoku. Since each row, column, and 3×3 box in a standard Sudoku must contain the digits 1 through 9 exactly once, the sum of any complete row, column, or box is always 45 (1+2+3+4+5+6+7+8+9 = 45).

This means if you know the sums of all cages in a row except one, you can calculate the missing cage's contribution by subtracting the known sums from 45. This technique is especially useful when a cage spans multiple rows or boxes.

Select a cage size using the toggle buttons above the table. The chart will display every valid sum for that cage size, along with all digit combinations that produce it.

Combinations marked as "Unique" have only one valid set of digits - these are solved immediately once you identify the cage. When playing, cross-reference this table with the digits already placed in the same row, column, or box to narrow down possibilities.

In a typical Killer Sudoku puzzle, cage sizes are not evenly distributed. Most published puzzles lean heavily toward smaller cages because they give the solver more direct information.

2-cell cages are the most common, usually making up 40-50% of all cages in a puzzle. They're the easiest to work with since each sum has at most 4 possible digit pairs.

3-cell cages are the second most common at roughly 25-35% of cages. They're still manageable but require more cross-referencing with row and column constraints.

4-cell and 5-cell cages appear occasionally, usually 2-5 per puzzle. Cages of 6+ cells are rare in standard difficulty puzzles, though expert-level Killer Sudoku may include them.

Harder puzzles tend to use larger cages with mid-range sums, since these have the most possible combinations and give away less information.