Kakuro is a number crossword puzzle that combines the logic of Sudoku with the structure of a crossword. Often called “cross sums,” it’s one of the most popular logic puzzles in Japan and has been gaining worldwide popularity as puzzle enthusiasts discover its elegant blend of arithmetic and deduction. Fill in digits 1 through 9 so that each horizontal and vertical group of cells adds up to the given clue number — with no digit repeated within any group.
The puzzle grid looks like a crossword, with white cells to fill and dark cells containing clue numbers. Each clue number sits in a divided dark cell: the number in the upper-right tells you the sum for the horizontal run of white cells to its right, and the number in the lower-left tells you the sum for the vertical run below. Your job is to figure out which combination of digits 1-9 produces each sum, then use the intersecting constraints to determine the exact placement.
What makes Kakuro deeply satisfying is how arithmetic constraints create logical deductions. Consider a clue of 3 in a two-cell run — the only possibility is 1+2, so those cells must contain 1 and 2 in some order. A clue of 17 in a two-cell run must be 8+9. These definite combinations are your starting points. As you fill in confirmed digits, the intersecting runs provide additional constraints that cascade through the puzzle. Advanced techniques involve tracking possible digit sets for each run and finding contradictions — much like advanced Sudoku solving.
The online version at kakuros.com offers puzzles in multiple sizes from 3×3 beginner grids to massive 30×30 expert challenges. Each puzzle has a unique solution that can be reached through pure logic — no guessing required. The clean interface lets you pencil-mark possible digits, highlight related cells, and check your progress. New puzzles are generated regularly, providing an endless supply of challenges at every difficulty level.
How To Play Kakuro
- Click an empty white cell and type a digit from 1 to 9.
- Each horizontal and vertical group of cells must add up to the clue number in the dark cell.
- No digit can repeat within a single horizontal or vertical group.
- Start with runs that have only one possible combination (like sum 3 in two cells = 1+2).
- Use intersecting constraints to narrow down possibilities for each cell.
- Choose your difficulty level — smaller grids are easier, larger ones are more challenging.
