Overview

Kakuro

1 player · 5-30 min per session

Fill every empty cell with digits 1-9 so that each across and down run matches its clue sum without repeating a digit inside the same run.

Players: 1P Session length: 5-30 min

PuzzleNumber

Goal & Core Rules

Fill every empty cell with digits 1-9 so that each across and down run matches its clue sum without repeating a digit inside the same run.

In a clue cell, the upper-right number is the across sum for the run to the right, and the lower-left number is the down sum for the run below.
Each run uses digits 1-9, and a digit may not repeat inside the same run.
Every playable cell must satisfy both its across run and its down run at the same time.
The current implementation includes four size-based difficulties, plus hint and export features.

Classic

Standard Kakuro rules with sum clues and no repeated digits in a run.

Size Difficulties

Boards scale from 6×6 on easy to 9×9 on expert, increasing density and deduction depth.

Controls

Mouse

Click a cell to select it
Use the on-screen number pad or keyboard digits 1-9 to enter
Use the top menu for hint, new game, export, and help

Keyboard

1-9: enter a digit
0 / Backspace / Delete: clear the selected cell

Touch

Tap a cell to select it
Use the bottom or side number pad to enter digits
Use Clear or Hint to erase a value or fill one empty cell correctly

Beginner Tips

Start with sums that have very few combinations. For example, 3 in two cells can only be 1+2.
Use intersections: a cell shared by a tight across run and a tight down run often becomes forced early.
Check the no-repeat rule before doing heavier sum math; it removes many candidates immediately.

Advanced Tips

Memorize common sum sets for 2-4 cell runs to prune options quickly.
When stuck, return to the most constrained run and compare it against crossing runs.
Use hints sparingly; it is usually better to narrow candidates from sum and repeat constraints first.

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

Sources

FAQ

Can a digit repeat in the same run?

No. Within any single across or down run, digits 1-9 must all be different.

How do I enter values on mobile?

Tap a cell to select it, then use the on-screen number pad. Clear and Hint are also available directly in the control panel.

What should I learn first?

Start with common 2-3 cell sum combinations and how crossing runs eliminate candidates.