Mouse
- Click a cell to select
- Enter a digit using keyboard or on-screen pad
- Toggle notes to add/remove candidates (if supported)
Overview 
Kakuro
카쿠로
A “mathematical crossword”: fill digits 1–9 so each run sums to its clue with no repeats.
Each clue is a tiny combinatorics puzzle. Crossings turn those small certainties into a full-grid solution.
Logic PuzzleNumber Puzzle
Goal & Core Rules
Fill all empty cells with digits 1–9 so that every horizontal and vertical run matches its clue sum without repeating a digit within the run.
- A clue cell gives the target sum for the run of white cells to its right (across) and/or below (down).
- Each run uses digits 1–9, and a digit may not repeat within the same run.
- Across and down runs intersect, so each cell’s digit must satisfy both sums simultaneously.
- Well-formed puzzles are designed to be solvable by logic rather than guessing.
Controls
Keyboard
- 1–9 to enter
- Backspace/Delete to clear
- N toggles notes (if supported)
- Arrow keys to move (if supported)
Touch
- Tap to select
- Use a number pad to enter
- Button/long-press to toggle notes (if supported)
Beginner Tips
- Start with runs whose sums have very few possible combinations (e.g., 3 in two cells must be 1+2).
- Use intersections: if a cell belongs to a constrained across run and a constrained down run, it often becomes forced.
- Write candidates only where it narrows choices—too many notes can slow you down.
Advanced Tips
- Memorize common sum sets for 2–4 cells to speed up deductions.
- When stuck, revisit the most constrained run and eliminate candidates via intersection conflicts.
- Look for ‘fixed digits’: a digit that appears in every valid combination for a run length/sum.
Origins & History
Kakuro is widely described as a number-based crossword. The English name “Cross Sums” was coined by Dell Magazines editor Jacob E. Funk (1966), while the Japanese name ‘Kakuro’ (an abbreviation meaning “addition cross”) became the globally common title. The puzzle later spread internationally via newspapers such as The Guardian.
Timeline
- 1966 Jacob E. Funk coins the English name “Cross Sums” (Dell Magazines).
- 2005 The Guardian introduces Kakuro to UK readers in its newspaper puzzle pages.
Notable People
- Jacob E. Funk Credited with coining the English name “Cross Sums” (Dell Magazines)
- Nikoli Japanese puzzle publisher associated with the puzzle’s popularity in Japan
FAQ
Can a digit repeat in the same run?
No. Within any single across or down run, digits 1–9 must be all different.
Is Kakuro a math test?
Not really—while you use sums, most progress comes from logic and combination constraints.
What should I learn first?
Common sum combinations for 2–3 cells and how intersections eliminate candidates.