How to play Kakuro
Kakuro, also called cross sums, has exactly two rules. Each line of white squares adds up to the clue at its start, and no digit repeats inside a line. Everything else in the game follows from those two sentences.
By Splash Logic · Updated 20 September 2026
The two rules
Rule 1: a line adds up to its clue
Fill white squares with the digits 1 to 9. A line of two squares with the clue 7 can be 2 and 5, or 3 and 4, or 1 and 6.
Rule 2: a digit never repeats inside a line
A line of two squares with the clue 4 must be 1 and 3. It cannot be 2 and 2, because that repeats the digit 2. There is no zero in Kakuro.
How to read a clue square
Clue squares are dark and split by a diagonal. The number in the top right belongs to the row running to the right of it. The number in the bottom left belongs to the column running down from it. A clue square can carry one number or both.
In this board, the top row of clues says: the left column adds to 3, the right column adds to 7. The left clues say: the top row adds to 4, the bottom row adds to 6.
Solving your first board, step by step
Step 1. Look at the left column: two squares adding to 3, with no repeat. The only option is 1 and 2, in some order.
Step 2. Look at the top row: two squares adding to 4. The options are 1 and 3, or 3 and 1. It cannot be 2 and 2.
Step 3. The top-left square belongs to both. It must be 1 or 2 (from the column) and 1 or 3 (from the row). Only 1 fits both.
Step 4. The rest follows. The top row is 1 and 3, the left column is 1 and 2, and the last square must be 4, which checks out: the bottom row is 2 + 4 = 6, and the right column is 3 + 4 = 7.
That move in step 3, using a row and a column together to narrow one square to a single digit, is called cross-referencing. It is the technique you will use most.
Do I need to be good at maths?
No. The sums are small additions with the digits 1 to 9. The work is logic: ruling options out until one remains. Many people who dislike arithmetic enjoy Kakuro for exactly that reason.
What to learn next
- The combinations cheat sheet: every total, and which sets of digits can make it. The single most useful page for a new player.
- The seven techniques: how experienced players break open a board.