Kakuro tips and combinations
Quick answer: learn the clues that allow only one set of digits (like 3 = 1+2 and 17 = 8+9 in two cells), start where those runs cross, and use the smallest or largest possible digits to narrow everything else.
Unique combinations chart
These clues can only be made one way. When you see one, you already know which digits the run contains, just not their order.
| Cells | Sum | Digits |
|---|---|---|
| 2 | 3 | 1 + 2 |
| 2 | 4 | 1 + 3 |
| 2 | 16 | 7 + 9 |
| 2 | 17 | 8 + 9 |
| 3 | 6 | 1 + 2 + 3 |
| 3 | 7 | 1 + 2 + 4 |
| 3 | 23 | 6 + 8 + 9 |
| 3 | 24 | 7 + 8 + 9 |
| 4 | 10 | 1 + 2 + 3 + 4 |
| 4 | 11 | 1 + 2 + 3 + 5 |
| 4 | 29 | 5 + 7 + 8 + 9 |
| 4 | 30 | 6 + 7 + 8 + 9 |
| 5 | 15 | 1 + 2 + 3 + 4 + 5 |
| 5 | 16 | 1 + 2 + 3 + 4 + 6 |
| 5 | 34 | 4 + 6 + 7 + 8 + 9 |
| 5 | 35 | 5 + 6 + 7 + 8 + 9 |
| 6 | 21 | 1 + 2 + 3 + 4 + 5 + 6 |
| 6 | 22 | 1 + 2 + 3 + 4 + 5 + 7 |
| 6 | 38 | 3 + 5 + 6 + 7 + 8 + 9 |
| 6 | 39 | 4 + 5 + 6 + 7 + 8 + 9 |
| 7 | 28 | 1 + 2 + 3 + 4 + 5 + 6 + 7 |
| 7 | 29 | 1 + 2 + 3 + 4 + 5 + 6 + 8 |
| 7 | 41 | 2 + 4 + 5 + 6 + 7 + 8 + 9 |
| 7 | 42 | 3 + 4 + 5 + 6 + 7 + 8 + 9 |
| 8 | 36 | 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 |
| 8 | 37 | 1 + 2 + 3 + 4 + 5 + 6 + 7 + 9 |
| 8 | 38 | 1 + 2 + 3 + 4 + 5 + 6 + 8 + 9 |
| 8 | 39 | 1 + 2 + 3 + 4 + 5 + 7 + 8 + 9 |
| 8 | 40 | 1 + 2 + 3 + 4 + 6 + 7 + 8 + 9 |
| 8 | 41 | 1 + 2 + 3 + 5 + 6 + 7 + 8 + 9 |
| 8 | 42 | 1 + 2 + 4 + 5 + 6 + 7 + 8 + 9 |
| 8 | 43 | 1 + 3 + 4 + 5 + 6 + 7 + 8 + 9 |
| 8 | 44 | 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 |
| 9 | 45 | 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 |
1. Cross the forced runs
Where two runs with known digit sets meet, the shared cell must hold a digit in both sets. Often only one digit qualifies.
2. Think high and low
A 2-cell run summing to 15 must be 6+9 or 7+8, so neither cell can be smaller than 6. Small clues keep big digits out; big clues keep small digits out. Use this to cross off options in the crossing runs.
3. The missing-digit trick
The digits 1–9 add up to 45. A run of 8 cells is missing exactly one digit: 45 minus the clue. A 9-cell run always sums to 45 and uses every digit.
4. Subtract known cells
Once you place a digit, subtract it from the run's clue. A 3-cell 12 with a 7 placed leaves 5 in two cells: 1+4 or 2+3.
5. Use the combination helper
On Puzzdoku, select any white cell to see the digit sets for its runs. Sets that clash with digits you've already placed are crossed out, which turns the techniques above into a quick visual check.
Frequently asked questions
Which Kakuro sums have only one combination?
For two cells: 3 (1+2), 4 (1+3), 16 (7+9) and 17 (8+9). For three cells: 6 (1+2+3), 7 (1+2+4), 23 (6+8+9) and 24 (7+8+9). For four cells: 10, 11, 29 and 30. The full list for every length is in the table on this page.
What's the fastest way to get better at Kakuro?
Memorise the unique combinations, then practise spotting where two runs with small digit sets cross. The shared cell is usually forced.
What is the 'missing digit' trick?
A run of 8 cells uses eight of the nine digits, so its clue tells you which one is missing: 45 minus the clue. For example, a 41 in 8 cells is every digit except 4.