Killer Sudoku

What is Killer Sudoku?

Killer Sudoku is a sudoku with almost no digits printed at the start. Instead, the grid is split into cages, groups of cells drawn with a dotted outline, and the corner of each cage carries the sum of its digits. The sudoku rules stay: in every row, column and 3 by 3 box, the digits 1 to 9 appear once each.

The game mixes sudoku logic with a little arithmetic. Every grid has exactly one answer, reached by reasoning and never by guessing. There are three levels, and every day brings a new grid, the same for everyone.

How to play Killer Sudoku

Tap a cell to select it, then tap a digit on the pad; tap the same digit again to take it out.

• Digits. In every row, column and 3 by 3 box, each digit from 1 to 9 appears exactly once.
• Cages. The digits in a cage add up to the sum in its corner and never repeat inside the cage, even when the cage crosses from one box into another.
• Mistakes. A repeated digit, or a cage that goes over or misses its sum, turns red.
• Notes. Turn on Notes to write small digits in a cell; a digit you place disappears from the notes in its row, column, box and cage.
• Score. Your score is the time to solve the grid, plus 30 seconds per hint. Each level has its own leaderboard.

Tips and strategy

1. Cages with one answer. A cage of 3 over two cells can only be 1 and 2, and one of 17 only 8 and 9. Start with those.
2. The 45 rule. A row, a column or a box always adds up to 45. Take away the cages lying wholly inside and you know the sum of the cells left over.
3. Combinations. A cage of 10 over three cells has few options: 1, 2, 7 or 1, 3, 6 or 1, 4, 5 or 2, 3, 5. A digit found in every option is certain to be in the cage.
4. Required digits. If a digit must be in a cage and the cage sits in a single row, that digit cannot appear anywhere else in that row.
5. Note early. On Hard, writing each cage's options as notes saves you redoing a lot of sums.

Frequently asked questions

Is Killer Sudoku free?

Yes. Like every game on Play, it runs free in your browser, with no download and no account.

How is it different from regular sudoku?

You do not start from given digits but from sums. The cages tell you what their digits add up to, and the rest is sudoku logic.

What does a hint do?

It first fixes a wrong digit if there is one, otherwise it places the digit reasoning reaches soonest. Each hint adds 30 seconds to your time.

What do the levels mean?

On Easy the cages are small and a few digits are given. On Medium cages have up to four cells, and on Hard up to five, with almost no digits given.

What is today's grid?

Every day everyone gets the same medium grid, so times compare directly on the leaderboard.