Every row, column and 3×3 box holds 1 to 9 once, and the digits in each dashed cage add up to its sum without repeating. Play today's puzzle or practise at three levels.
Getting today's puzzle ready…
How to play
Pick a cell. Its whole cage is highlighted, and the helper lists every set of digits that can still fill that cage.
Enter a number with the keypad or keys 1 to 9, or switch on Notes (N) to pencil in candidates.
Use the cage sums and the normal sudoku rules to narrow each cell down to one digit.
Fill the grid to finish. Wrong numbers are underlined if “Show mistakes” is on.
The rules
Each row, column and 3×3 box holds 1 to 9 once.
The digits in a cage add up to the number in its corner.
A digit can't appear twice in the same cage.
Worked example: cage combinations
Some cage sums can only be made one way, and those are the best places to start. These lists come from the same code as the helper in the game:
2 cells adding to 3: 1 + 2. Adding to 17: 8 + 9.
3 cells adding to 6: 1 + 2 + 3. Adding to 24: 7 + 8 + 9.
3 cells adding to 10 has four sets: 1 + 2 + 7, 1 + 3 + 6, 1 + 4 + 5, 2 + 3 + 5. If one cell must be 7 (for example, it's the last place for 7 in its row), the other two are 1 and 2.
Combine this with the 45 rule: if the cages wholly inside a box add up to 38, the one cell left over in that box must be 45 − 38 = 7.
Tips
Start with cages that have only one possible set, like a 3 or 17 in two cells, then use those digits to clear notes elsewhere.
Look for cages that stick out of a box by one cell: the 45 rule tells you that cell's value from the difference.
Fill all notes when you're stuck: they take cage sums into account, so impossible digits never appear.
New to sudoku? Start with the classic daily sudoku, which uses the same controls.
Frequently asked questions
What is killer sudoku?
It's sudoku without given numbers. Instead, the grid is split into cages outlined with dashed lines, each with a small sum in its corner. The digits in a cage must add up to that sum and can't repeat inside the cage, on top of the normal row, column and box rules.
Can a digit repeat inside a cage?
No. A cage never holds the same digit twice, even when the cage crosses from one box into another. That's why a two-cell cage of 4 has to be 1 and 3, not 2 and 2.
What is the 45 rule?
The digits 1 to 9 add up to 45, so every row, column and box adds up to 45. If the cages that sit wholly inside a box add up to 38, the box's remaining cells must add up to 7. Over two rows the total is 90, and over three rows 135.
Is every puzzle solvable without guessing?
Yes. Each puzzle is solved by a logic program before you see it, using only steps a person can make (cage combinations, the 45 rule, singles, pairs and triples). If that program gets stuck, the puzzle is changed until it doesn't, so every puzzle has exactly one solution.
What do the levels mean?
Easy uses small cages of two or three cells and solves with cage combinations and singles. Medium has bigger cages and needs the 45 rule or pairs. Hard has the biggest cages and needs the 45 rule across two or three rows or columns, or triples. The daily puzzle is Easy early in the week and Hard at the weekend.
