How to play kakuro
Kakuro looks like a crossword filled with numbers. Each white square takes a digit from 1 to 9. A horizontal or vertical line of white squares is called a run, and the clue for each run sits in the dark square just before it: the number in the upper right is the sum for the run going across, and the number in the lower left is the sum for the run going down.
- The digits in a run must add up to its clue.
- No digit may appear twice in the same run.
Select a square and type a digit, or use the number pad. Arrow keys jump between white squares. Notes (N key) adds small candidates, Hint fills one correct square, and Undo has no limit. A clue turns red when its run is complete with the wrong total or already goes over it.
Sizes
The small grid has a 6×6 playing area and short runs, good for learning. Medium (8×8) and large (10×10) grids have longer runs of up to six or seven squares and more places where runs cross, so you will lean on combinations and notes more.
Strategy tips
Memorize the one-way sums
Some sums can only be made one way. These are the keys that open most puzzles.
| Run length | Sum | Digits |
|---|---|---|
| 2 | 3, 4 | 1 2 and 1 3 |
| 2 | 16, 17 | 7 9 and 8 9 |
| 3 | 6, 7 | 1 2 3 and 1 2 4 |
| 3 | 23, 24 | 6 8 9 and 7 8 9 |
| 4 | 10, 11 | 1 2 3 4 and 1 2 3 5 |
| 4 | 29, 30 | 5 7 8 9 and 6 7 8 9 |
| 5 | 15, 35 | 1 2 3 4 5 and 5 6 7 8 9 |
Work the crossings
A square belongs to one across run and one down run, so its digit must fit both. If the across run is 4 in two squares (1 and 3) and the down run is 16 in two squares (7 and 9), there is a clash, which tells you to recheck. When one run allows 1 or 3 and the other allows 3 or 5, the square must be 3.
Use the size of the digits
A two-square run of 10 cannot hold a 5 (it would need two 5s). A long run with a small total must use the smallest digits, and one with a large total must use the biggest. These limits cut down your options quickly.
Where kakuro comes from
The puzzle was long printed in North American puzzle magazines under the name Cross Sums. The name kakuro comes from Japan, where it is short for a phrase meaning "addition cross." If you like this kind of arithmetic logic, Killer Sudoku uses the same combination tables inside a sudoku grid, and classic Sudoku needs no math at all.
Questions
Can I use 0 in kakuro?
No. Only the digits 1 to 9 are used, and a digit cannot repeat within the same run.
Can a digit repeat in a row of the grid?
Yes, as long as the two copies are in different runs, separated by a dark square. The no-repeat rule only applies inside one run.
Does each puzzle have only one solution?
Yes. Every grid was checked by a solver before it was added, and only grids with exactly one solution are used.
What does the sum helper do?
It lists every combination of different digits that fits the across and down runs of the selected square, crosses out sets that clash with digits already placed, and shows which digits can still go in that square.