➕ How to play Killer Sudoku

By Miguel Arechaga

Killer Sudoku combines the best of classic Sudoku with a touch of arithmetic. There isn't a single clue number: the entire board is solved from the cages and their sums. It's a delightful challenge for anyone who already has a handle on regular Sudoku. Here we explain the rules and the key tricks to solve it.

What is Killer Sudoku?

It's a Sudoku variant where the board is divided into cages (groups of cells marked with a dotted border). Each cage carries a small number showing the sum of its cells. It's played with no starting clue numbers.

Rules and how to play step by step

1. The Sudoku rules apply: 1 through 9 with no repeats in any row, column, or 3x3 box.
2. The numbers in each cage must add up to the value shown in its corner.
3. Within a single cage, no number can repeat.
4. Every puzzle has a unique solution, reachable through logic alone.

Tricks to solve Killer Sudoku

• Unique sum combinations: some sums can only come out one way. For example, two cells summing to 3 are 1 and 2; summing to 17 are 8 and 9; three cells summing to 6 are 1, 2 and 3.
• The rule of 45: every row, column and box always sums to 45 (1+2+...+9). If almost every cage in an area falls inside it, you can deduce the missing cell.
• Start with cages that have a very low or very high sum: they have the fewest possible options.
• Combine the arithmetic with classic Sudoku elimination: every number you place opens up new deductions.

How it differs from regular Sudoku

Compared to classic Sudoku, Killer adds the layer of sums, which makes it more demanding and addictive. If you like numbers, you'll also love Kakuro. It's ideal for practicing advanced Sudoku techniques with an extra twist.

🏆 Time ranking

Killer Sudoku has its own global ranking: your best time solving the grid is saved. Go to Ranking, the 🕹️ 1 Player tab, choose "Killer Sudoku" from the dropdown, and compare your score with other players, synced to your account. For your result to count you need a free account on MundoSudoku (just a username and password, no email required): you can play without one, but without logging in your score won't be saved to the ranking.