Killer Sudoku rules and puzzles

The case notes

What a Killer cage means

Learn Killer Sudoku cage rules with a worked example: add the digits to the clue, avoid repeats, then use a column to place them.

Put it into practice

What does a Killer cage mean?

Normal Sudoku rules still apply: each row, column and box contains the digits 1 to 9 once. The digits inside a dotted cage add up to its small clue. A digit cannot repeat anywhere in the same cage.

Find the set, then the order

A two-cell cage totalling 3 contains 1 and 2. The sum alone does not tell you which cell holds each digit. A 1 already in a column rules out 1 from the cage cell in that column, so that cell must be 2.

Why repeats matter

A two-cell cage totalling 4 cannot contain 2 and 2. It must contain 1 and 3. The no-repeat rule applies to every cage, including cages that cross a box boundary.

Read the transcript

This is a nine by nine Sudoku. A Killer cage has a dashed outline and a small number. That clue is the total for the cells inside. This cage has two cells and a clue of three. Only one and two add to three using Sudoku digits. This second cage sums to four. Two and two would add to four, but a Killer cage cannot repeat a digit. It must use one and three. Now use the ordinary Sudoku rules. There is already a one in this column, so this cage cell cannot be one. It must be two. Two is placed. The cage still needs one to reach three. Start with the sum, then combine it with the row, column and box rules.

Keep following the clues