Killer Sudoku
Combine sum cages with the familiar Sudoku rules.
Stuck, or just getting started? Let’s practise ↓
No repeats in any row, column or box
Take a breather
Your game will be here when you return
Tap to note, again to eliminate, and once more to restore
Use 1–9 to enter numbers
and arrow keys to select a cell
Your journey
Finish each stage to unlock the next
PLAY · NOTICE · TRY
One small move at a time.
Pick a step below. You can try, get it wrong and start again. Your saved game stays here.
Start with the row, column or box that has the most numbers
Fewer empty cells can make the next answer easier to spot
Killer Sudoku — rules and practice
Every row, column and 3×3 box still contains the digits 1–9 without repetition. Dashed outlines add cages: the small number is the sum of the cells inside, with no repeated digit in the same cage. Some Sudoku-Y puzzles include starting digits to help you begin.
A box is different from a cage
A box is the fixed 3×3 area bounded by thicker grid lines. A cage can have a different shape and cross box boundaries. A placement must satisfy all row, column, box and cage constraints. Select a cell to see the sum already entered and the remaining sum for its cage.
Start with a cage that has one empty cell
A two-cell cage totaling 11 with a 4 already entered needs a 7 in its other cell: 11−4=7. With both cells empty, the possible sets include {2,9}, {3,8}, {4,7} and {5,6}. Knowing a set does not establish its order; use the other constraints to decide the positions.
Apply the rule of 45 to the exact area
Digits 1–9 sum to 45 in every complete row, column or box. If cages fully contained in a row cover eight cells and total 39, the ninth cell is 6. If a cage extends outside that row, subtracting its entire total would include cells outside the area you meant to count.
Try a small example
An original two-cell cage example totals 11 and already contains 4. What is the other value?
Show reasoning
7, because 11−4=7 and the two values are distinct. In a full puzzle, check the row, column and box too. This partial example illustrates a cage remainder.
Common questions
Do I need advanced mathematics?
No. The arithmetic is mainly small sums and subtraction. The challenge is narrowing the allowed sets and determining their positions.
Can I change the board size?
Yes. The size picker also offers Killer 4×4, 6×6 and 16×16. A complete unit then sums to 10, 21 or 136 respectively, instead of 45.