Kakuro
Fill the grid so each entry's digits add up to the clue number. No digit repeats within an entry. Clue cells show across sums (bottom-left) and down sums (top-right).
Kakuro
Small grids (6–8). Short entries. Learn sum logic.
Standard play. Timer runs. Hints available.
What is kakuro?
Kakuro (sometimes called cross sums) is a number puzzle that combines elements of crosswords and sudoku. The grid contains black cells and white cells. Black cells with diagonal lines hold clue numbers: the number below-left is the sum for the horizontal entry, and the number above-right is the sum for the vertical entry. Your job is to fill every white cell with a digit from 1 to 9 so that each entry adds up to its clue, with no repeated digits within any entry.
Unlike sudoku, kakuro grids vary in size and shape. Easy puzzles use 6x6 or 8x8 grids, while harder puzzles may be 12x14 or larger. The constraint is always the same: digits in an entry must sum to the clue and cannot repeat. Every puzzle has exactly one solution, and every puzzle on this site is solvable through logic alone.
How to play
Tap a white cell to select it, then tap a number (1-9) to place it. The clue cells show sums separated by a diagonal line: bottom-left for across entries, top-right for down entries. When you select a cell, its entries highlight so you can see which cells share the same clue.
Use notes mode to track candidate digits. The hint system will point you toward a solvable cell with an explanation of the technique used. If you get completely stuck, reveal the solution and study which technique would have unlocked the next step.
Play modes
Classic
Timer runs up. Up to 3 hints. Undo available. The default way to play.
Timed Trial
Beat the countdown. Time limit scales with difficulty: 10 min for easy, 4 min for einstein.
Challenge
No hints. No undo. Every digit placement is permanent.
How to solve kakuro
Technique by technique, beginner to advanced.
Forced combinations
Two-cell entries with extreme sums have only one valid combination. Sum 3 is always 1+2. Sum 4 is always 1+3. Sum 16 is always 7+9. Sum 17 is always 8+9. Memorizing these gives you instant placements at every level.
Three-cell entries work similarly at the extremes. Sum 6 is always 1+2+3. Sum 24 is always 7+8+9. For mid-range sums you'll have multiple combinations, but cross-entry constraints usually narrow them quickly.
Cross-entry elimination
Every white cell belongs to exactly one across entry and one down entry. The valid digits for a cell are the intersection of what both entries allow. When an across entry restricts a cell to {1, 2, 4} and the down entry restricts it to {2, 5, 7}, the cell must be 2.
Combination filtering
For each entry, list every valid digit combination that sums to the clue. Then cross out combinations that conflict with digits already placed in crossing entries. If only one combination survives, every cell in that entry is determined.
Even when multiple combinations remain, look for digits common to all surviving combinations. If every valid combination includes the digit 5, then 5 must appear somewhere in that entry.
Naked singles
When a cell has only one remaining candidate after all elimination, place that digit. This often triggers a chain reaction: filling one cell reduces candidates in crossing entries, creating new naked singles elsewhere.