The grid
A Kakuro grid looks like a crossword made of numbers. The white cells are the ones you fill in, each taking a single digit from 1 to 9. The black cells are dividers, and some of them carry clues.
Reading the clues
A clue is a number printed inside a black cell, split by a diagonal line:
- A number in the top-right is the target sum for the run of white cells running to the right.
- A number in the bottom-left is the target sum for the run of white cells running downward.
A run is simply the unbroken line of white cells between two black cells. Every run has exactly one clue at its start.
The two rules
- Each run sums to its clue. Add the digits in a run and they must equal the number in the clue cell.
- No digit repeats within a run. A run can use any of 1 to 9, but never the same digit twice. (It may reappear in a different run.)
That is the entire rulebook. Everything else is deduction.
Your first moves
The trick to starting is to find runs with only one possible combination of digits. Because Kakuro uses only 1 to 9, the extremes are fixed:
- A two-cell run summing to 3 can only be 1 and 2.
- A two-cell run summing to 4 can only be 1 and 3.
- A two-cell run summing to 16 can only be 7 and 9.
- A two-cell run summing to 17 can only be 8 and 9.
- A three-cell run summing to 6 can only be 1, 2 and 3.
- A three-cell run summing to 24 can only be 7, 8 and 9.
You may not know the order yet, but you know the digits. Where one of these runs crosses another, the crossing cell must be a digit common to both, which often pins it down completely. The full set of locked combinations is on the combinations page.
Working outward
Once a cell is fixed, it constrains every run it belongs to. Cross off that digit as an option in the crossing run, recompute what is left, and look for the next cell with only one possibility. Good Kakuro is a chain of these small certainties. Use the on-screen notes feature to pencil in candidates, exactly as you would on paper.
Finishing
When every white cell is filled and every run hits its clue with no repeats, the puzzle is solved. Our game checks this for you automatically and times your solve. Ready? Start with an easy grid and work up.
Frequently asked questions
What do the two numbers in a black cell mean?+
A black cell can hold up to two clues split by a diagonal. The number in the top-right is the sum for the run of white cells to its right. The number in the bottom-left is the sum for the run of white cells going down from it.
Can a digit repeat in Kakuro?+
Not within a single run. Each horizontal run and each vertical run must use distinct digits from 1 to 9. The same digit can appear elsewhere in the grid, just not twice in the same run.
Is zero ever used in Kakuro?+
No. Kakuro uses only the digits 1 through 9. That is why a two-cell run can never sum to less than 3 (which is 1 plus 2) or more than 17 (which is 8 plus 9).
Where should a beginner start a Kakuro puzzle?+
Start with the most constrained runs: short runs with extreme sums. A two-cell run summing to 3 must be 1 and 2, and one summing to 17 must be 8 and 9. These locked digits give you footholds to work outward.