Kakuro Puzzle Rules: The Complete Reference
A quick-reference page for Kakuro rules. Pin it, bookmark it, or print it out. Everything you need on one page.
Kakuro rules are short. The hard part is getting good at them, not learning them. Here is the full list of rules on one page. Print it. Pin it. Use it when you are stuck.
The four core kakuro rules
Rule one: Fill each white cell with a digit from 1 to 9.
Rule two: The digits in each run (across or down) must add up to the small clue number in the dark cell at the start of that run.
Rule three: No digit can repeat inside the same run. (Digits can repeat across the grid as long as not in the same run.)
Rule four: Each puzzle has exactly one valid answer.
How to read a kakuro grid
Dark cells are clue cells. Light cells are answer cells. Each dark cell may show a number in its upper right (for the across run that starts to its right) or lower left (for the down run that starts below).
Some dark cells show both. Some show only one. Some show neither (those are just spacers).
Common kakuro terms
Run: a line of connected white cells, all going one direction.
Clue: the sum target shown in a dark cell.
Combination: the set of digits that can add up to a clue without repeats.
Pencil mark: a small candidate digit you write inside a cell while you work.
Locked combo: a sum-and-length pair that has only one possible set of digits (like sum 6 in 3 cells, which must be 1, 2, 3).
What is not a kakuro rule
You do not need to fill the whole grid before checking. You can spot-check a single run any time.
You do not need to fill in order. Skip cells you cannot solve and come back.
Pencil marks are not part of the official rules. They are a tool. Use them or skip them.
Where to play by these kakuro game rules
KakuroZen.com runs the rules in real-time. Make a wrong move and the cell turns red. Newer to the game? Pick the easy level. The app shows tips.
The KakuroZen books print the rules on page one of every edition. So you always have them handy.