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Killer Sudoku Online

A sudoku with an extra twist: the grid is split into dotted cages with a sum in the corner, and the numbers in each cage can't repeat and must add up to that sum. Four levels, notes, hints and a combinations chart so you don't have to work it out from memory. Free, no sign-up.

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Select a cell and tap a number. Cages are the groups with a dotted border, and the sum is in the top-left corner of each one; single-cell cages come already solved. With Notes turned on you jot down candidates. On a computer you can also use the keyboard: arrow keys, numbers, Delete, N for notes and Z to undo.

Cage combinations chart (2 to 5 cells)
2 cells
SumCombinations
31-2
41-3
51-4 2-3
61-5 2-4
71-6 2-5 3-4
81-7 2-6 3-5
91-8 2-7 3-6 4-5
101-9 2-8 3-7 4-6
112-9 3-8 4-7 5-6
123-9 4-8 5-7
134-9 5-8 6-7
145-9 6-8
156-9 7-8
167-9
178-9
3 cells
SumCombinations
61-2-3
71-2-4
81-2-5 1-3-4
91-2-6 1-3-5 2-3-4
101-2-7 1-3-6 1-4-5 2-3-5
111-2-8 1-3-7 1-4-6 2-3-6 2-4-5
121-2-9 1-3-8 1-4-7 1-5-6 2-3-7 2-4-6 3-4-5
131-3-9 1-4-8 1-5-7 2-3-8 2-4-7 2-5-6 3-4-6
141-4-9 1-5-8 1-6-7 2-3-9 2-4-8 2-5-7 3-4-7 3-5-6
151-5-9 1-6-8 2-4-9 2-5-8 2-6-7 3-4-8 3-5-7 4-5-6
161-6-9 1-7-8 2-5-9 2-6-8 3-4-9 3-5-8 3-6-7 4-5-7
171-7-9 2-6-9 2-7-8 3-5-9 3-6-8 4-5-8 4-6-7
181-8-9 2-7-9 3-6-9 3-7-8 4-5-9 4-6-8 5-6-7
192-8-9 3-7-9 4-6-9 4-7-8 5-6-8
203-8-9 4-7-9 5-6-9 5-7-8
214-8-9 5-7-9 6-7-8
225-8-9 6-7-9
236-8-9
247-8-9
4 cells
SumCombinations
101-2-3-4
111-2-3-5
121-2-3-6 1-2-4-5
131-2-3-7 1-2-4-6 1-3-4-5
141-2-3-8 1-2-4-7 1-2-5-6 1-3-4-6 2-3-4-5
151-2-3-9 1-2-4-8 1-2-5-7 1-3-4-7 1-3-5-6 2-3-4-6
161-2-4-9 1-2-5-8 1-2-6-7 1-3-4-8 1-3-5-7 1-4-5-6 2-3-4-7 2-3-5-6
171-2-5-9 1-2-6-8 1-3-4-9 1-3-5-8 1-3-6-7 1-4-5-7 2-3-4-8 2-3-5-7 2-4-5-6
181-2-6-9 1-2-7-8 1-3-5-9 1-3-6-8 1-4-5-8 1-4-6-7 2-3-4-9 2-3-5-8 2-3-6-7 2-4-5-7 3-4-5-6
191-2-7-9 1-3-6-9 1-3-7-8 1-4-5-9 1-4-6-8 1-5-6-7 2-3-5-9 2-3-6-8 2-4-5-8 2-4-6-7 3-4-5-7
201-2-8-9 1-3-7-9 1-4-6-9 1-4-7-8 1-5-6-8 2-3-6-9 2-3-7-8 2-4-5-9 2-4-6-8 2-5-6-7 3-4-5-8 3-4-6-7
211-3-8-9 1-4-7-9 1-5-6-9 1-5-7-8 2-3-7-9 2-4-6-9 2-4-7-8 2-5-6-8 3-4-5-9 3-4-6-8 3-5-6-7
221-4-8-9 1-5-7-9 1-6-7-8 2-3-8-9 2-4-7-9 2-5-6-9 2-5-7-8 3-4-6-9 3-4-7-8 3-5-6-8 4-5-6-7
231-5-8-9 1-6-7-9 2-4-8-9 2-5-7-9 2-6-7-8 3-4-7-9 3-5-6-9 3-5-7-8 4-5-6-8
241-6-8-9 2-5-8-9 2-6-7-9 3-4-8-9 3-5-7-9 3-6-7-8 4-5-6-9 4-5-7-8
251-7-8-9 2-6-8-9 3-5-8-9 3-6-7-9 4-5-7-9 4-6-7-8
262-7-8-9 3-6-8-9 4-5-8-9 4-6-7-9 5-6-7-8
273-7-8-9 4-6-8-9 5-6-7-9
284-7-8-9 5-6-8-9
295-7-8-9
306-7-8-9
5 cells
SumCombinations
151-2-3-4-5
161-2-3-4-6
171-2-3-4-7 1-2-3-5-6
181-2-3-4-8 1-2-3-5-7 1-2-4-5-6
191-2-3-4-9 1-2-3-5-8 1-2-3-6-7 1-2-4-5-7 1-3-4-5-6
201-2-3-5-9 1-2-3-6-8 1-2-4-5-8 1-2-4-6-7 1-3-4-5-7 2-3-4-5-6
211-2-3-6-9 1-2-3-7-8 1-2-4-5-9 1-2-4-6-8 1-2-5-6-7 1-3-4-5-8 1-3-4-6-7 2-3-4-5-7
221-2-3-7-9 1-2-4-6-9 1-2-4-7-8 1-2-5-6-8 1-3-4-5-9 1-3-4-6-8 1-3-5-6-7 2-3-4-5-8 2-3-4-6-7
231-2-3-8-9 1-2-4-7-9 1-2-5-6-9 1-2-5-7-8 1-3-4-6-9 1-3-4-7-8 1-3-5-6-8 1-4-5-6-7 2-3-4-5-9 2-3-4-6-8 2-3-5-6-7
241-2-4-8-9 1-2-5-7-9 1-2-6-7-8 1-3-4-7-9 1-3-5-6-9 1-3-5-7-8 1-4-5-6-8 2-3-4-6-9 2-3-4-7-8 2-3-5-6-8 2-4-5-6-7
251-2-5-8-9 1-2-6-7-9 1-3-4-8-9 1-3-5-7-9 1-3-6-7-8 1-4-5-6-9 1-4-5-7-8 2-3-4-7-9 2-3-5-6-9 2-3-5-7-8 2-4-5-6-8 3-4-5-6-7
261-2-6-8-9 1-3-5-8-9 1-3-6-7-9 1-4-5-7-9 1-4-6-7-8 2-3-4-8-9 2-3-5-7-9 2-3-6-7-8 2-4-5-6-9 2-4-5-7-8 3-4-5-6-8
271-2-7-8-9 1-3-6-8-9 1-4-5-8-9 1-4-6-7-9 1-5-6-7-8 2-3-5-8-9 2-3-6-7-9 2-4-5-7-9 2-4-6-7-8 3-4-5-6-9 3-4-5-7-8
281-3-7-8-9 1-4-6-8-9 1-5-6-7-9 2-3-6-8-9 2-4-5-8-9 2-4-6-7-9 2-5-6-7-8 3-4-5-7-9 3-4-6-7-8
291-4-7-8-9 1-5-6-8-9 2-3-7-8-9 2-4-6-8-9 2-5-6-7-9 3-4-5-8-9 3-4-6-7-9 3-5-6-7-8
301-5-7-8-9 2-4-7-8-9 2-5-6-8-9 3-4-6-8-9 3-5-6-7-9 4-5-6-7-8
311-6-7-8-9 2-5-7-8-9 3-4-7-8-9 3-5-6-8-9 4-5-6-7-9
322-6-7-8-9 3-5-7-8-9 4-5-6-8-9
333-6-7-8-9 4-5-7-8-9
344-6-7-8-9
355-6-7-8-9

How to play Killer Sudoku

  1. Fill the 9×9 grid so that every row, column and 3×3 box contains the numbers 1 to 9 without repeating, just like in a regular sudoku.
  2. The grid is divided into cages with a dotted border. The small number in the top-left corner of each cage is the sum its cells must add up to.
  3. Numbers can't repeat inside a cage. A single-cell cage comes already solved: the sum is the number.
  4. Use the combinations chart (or the help that appears when you select a cell) to see which sets of digits make each sum, jot down candidates with Notes and keep going. Every board has exactly one solution.

What Killer Sudoku is and how to solve it

Killer Sudoku (also called sum sudoku) mixes sudoku with an addition puzzle: it gives you almost no starting numbers and instead tells you the sum of each cage. Since the digits in a cage never repeat, each sum has only a few possible combinations, and that is where the logic comes from. Two cells adding up to 3 can only be 1 and 2; three cells adding up to 7 can only be 1-2-4; two cells adding up to 17 are 8 and 9; three cells adding up to 24 are 7-8-9. With four cells, 10 is always 1-2-3-4.

The most useful strategy is the 45 rule: every row, column and box adds up to 45, so if an area is made of whole cages plus one or two loose cells, the difference tells you the value of those cells. Combine it with notes: cross out candidates that don't belong to any possible combination and look for the digit that is forced into a cell.

The levels change the cage size (bigger cages and fewer givens = harder) and the number of given digits: Easy gives up to 12, Medium about 6, Hard about 2 and Expert almost none. Everything is built on your device, the solution is unique and it is verified before the board is shown to you. The combinations chart on this page covers cages of 2 to 5 cells.

Good to know

Frequently asked questions

What is Killer Sudoku?

A sudoku where the grid is divided into cages with a sum. On top of the usual rules (1 to 9 without repeating in rows, columns and boxes), the numbers in each cage don't repeat and add up to the number shown.

What are the combinations for a cage?

It depends on the sum and the number of cells: two cells adding up to 3 are 1-2, three cells adding up to 7 are 1-2-4 and four cells adding up to 10 are 1-2-3-4. See the combinations chart on the page for all of them, from 2 to 5 cells.

What is the 45 rule?

Every row, column and box adds up to 45 (1+2+…+9). If an area is made of complete cages plus one or two loose cells, subtracting the cage sums from 45 tells you what the loose cells are worth.

Does every board have only one solution?

Yes. It is checked when the board is generated; if needed, cages are split or a number is given as a clue until the solution is unique, so you never have to guess.

Can numbers repeat inside a cage?

No. Inside a cage all numbers are different, and that is what lets you work out the combinations.

Is it free? Is my game saved?

It's free, needs no sign-up and runs in your browser. The game in progress and your best times are saved only on your device.