A Kakuro solver built around real crossing runs
Kakuro combines the arithmetic of a crossword with the no-repeat rule of Sudoku. Each white cell belongs to one horizontal run and one vertical run. The digits in a run add to its clue total, and no digit can appear twice within that single run. A helpful Kakuro solver has to respect both directions at the same time: a digit that works for one total may fail once its crossing total is considered.
This free online Kakuro solver lets you model that connection without drawing a full black-and-white board. Give each white square a short label, such as A1 or B3. Put the labels in every matching across and down run, then solve. The result lists the digit for each label. This input method is especially convenient when a large puzzle only has one stubborn region; describe that connected region rather than manually recreating every black clue cell.
Think in shared labels: if the same white square is touched by an across and a down clue, it must use exactly the same label in both lists. A spelling difference creates two different cells.
Enter a Kakuro puzzle in three reliable steps
Label the target white cells
Use short unique labels. A1, A2, B1, and B2 are easy to read, but any label beginning with a letter works. You do not need to write these labels in the original puzzle. They are a private map for the helper. Start with a connected group so each cell has an across and down membership.
Add every across run
For each horizontal segment, enter its clue total and the labels in left-to-right order. A run with total 16 and cells A1, A2, A3 says that three distinct digits in those cells must add to 16. The cell order makes the result easier to transfer back, although the arithmetic rule itself is about the set of digits.
Add every down run with the same labels
Repeat for vertical segments, using the same label at each crossing. The page validates that a cell occurs exactly once in each direction. If A2 is included in two across runs, or no down run, the input is not a standard Kakuro grid and the status text tells you what to repair.
How the Kakuro helper narrows digit combinations
First, the solver lists possible ordered digit patterns for every total and run length. A two-cell sum of 3 can only be 1 and 2 in either order; a two-cell sum of 17 can only be 8 and 9. Longer totals allow more combinations, but none may repeat a digit. The solver then compares the possible values of each shared label across its horizontal and vertical runs, eliminating combinations that disagree.
The crossing constraints compound quickly. For example, a cell that could be 2, 5, or 7 in its across run may be limited to 5 by its down run. Once that value is fixed, both runs lose possibilities. The output is a valid fill for the runs you entered. If several fills are possible, the page tells you rather than claiming a unique completion.
Kakuro sum combinations that help manual solving
Some totals are strong before you use any tool. A two-cell 3 is always 1+2, and a two-cell 17 is always 8+9. A two-cell 4 is 1+3; a two-cell 16 is 7+9. For three cells, total 6 must be 1+2+3, while total 24 must be 7+8+9. These are digit sets, not positions: crossings decide which digit belongs to which cell. Recognizing them gives you fast starting candidates.
Do not make the common mistake of allowing repeated digits in a run. A clue total of 10 across two cells cannot be 5+5. It may be 1+9, 2+8, 3+7, or 4+6, in either order. The Kakuro solver enforces that rule automatically, but knowing it helps catch transcription errors in the original grid.
Fix these common Kakuro input errors
“Must appear in exactly one across and one down run.” Find that label in both lists. You may have forgotten a crossing run, used a different spelling such as A-1 instead of A1, or entered a label twice in the same direction.
“No valid fill.” Check each total against its run length, then verify every shared label. An accidental total, a missing cell, or a repeated label makes the combined equations impossible. Start with a small connected group if a full puzzle is hard to audit.
“More than one answer.” The described area may not include enough crossings to force a unique result. Add the next run that connects to the uncertain cells. A valid Kakuro puzzle normally becomes unique only with all relevant clue runs present.
Use this online Kakuro solver as a check, not a black box
A good workflow is to make the obvious sum deductions yourself, then use the tool to check a difficult intersection. Transfer the output to the original board and ask whether it opens another short run. That keeps the puzzle enjoyable while avoiding time lost on an arithmetic contradiction. On a phone, take note of just the labels and sums around one area; there is no need to upload a photograph.
All calculation happens locally in this browser. It requires neither registration nor a downloaded app. If you want a different number puzzle after finishing, explore the related Minesweeper Solver or logic-grid tools on this site.
Frequently asked questions
Can I enter only part of a Kakuro grid?
Yes, if it is a complete connected sub-grid: every included white cell needs one across and one down run. Add nearby runs when the partial area has multiple solutions.
Why do labels need to begin with a letter?
The simple label format prevents ambiguity with sum values and makes each white cell easy to identify. Labels such as A1, B12, and Cell7 work.
Does this Kakuro solver repeat digits?
No. It follows the standard Kakuro rule that digits 1–9 cannot repeat within a single across or down run.