Killer Sudoku for Beginners: Rules and How to Play
By Michel ·
Sudoku a Day Blog
Killer Sudoku combines the usual placement rules with cage sums. This guide explains the extra rule and a few ways to begin; difficulty depends on the individual puzzle.
What Is Killer Sudoku?
Killer Sudoku is a variant of standard Sudoku. The grid is the same: 9×9, divided into nine 3×3 boxes. The extra rule uses "cages"—groups of outlined cells with a target sum. Many Killer puzzles have no given digits, but some include them; follow the instructions for your puzzle.
Each cage has a small number in the corner. That number is the sum of all the digits in that cage. For example, if a cage of two cells has a "9" in the corner, those two cells must add up to 9.
The Rules
1. Every row must contain the numbers 1-9 exactly once.
2. Every column must contain the numbers 1-9 exactly once.
3. Every 3×3 box must contain the numbers 1-9 exactly once.
4. Every cage must sum to the number shown in its corner.
5. No number can repeat within a cage.
How to Get Started
Start with the smallest cages. A cage of one cell always equals its sum—place that number immediately.
Every complete row, column and box totals 45 (1+2+3+4+5+6+7+8+9). If whole cages lie entirely inside one unit and cover eight of its cells, subtract their totals from 45 to find the uncovered cell.
For example, if those whole cages total 39, the ninth cell is 45−39=6. Do not subtract the full total of a cage that extends outside the unit: only its cells inside the unit belong to that total of 45.
Tips for Beginners
1. Use candidate notes when helpful. Place a proven digit directly, or record possibilities after checking rows, columns, boxes and cage sums. Update notes after each deduction.
2. Cage digits cannot repeat. A two-cell cage totaling 9 can use 1/8, 2/7, 3/6 or 4/5 before other constraints are applied. A cage need not contain all nine digits.
3. Start with 45. Look for opportunities to use the 45 rule on rows, columns, or boxes with known cage sums.
Try It Today
Start with a puzzle intended for beginners and check its cage rules carefully. Adding sums changes the deductions; it does not make every Killer puzzle harder than every standard Sudoku.
Read our illustrated Killer Sudoku rules and example. Our daily player and printable packs use standard Sudoku; this link opens a learning guide, not playable Killer puzzles.