Play Kakuro Online

Fill every run of white cells so the digits sum to the clue — using only 1–9 with no repeats per run. A mathematical crossword you can solve with pure logic.

Timer
00:00
Progress
0 / 0

Tap a white cell, then enter a digit

Puzzle Solved!

What Is Kakuro?

Kakuro (also written Cross Sums) is a logic-based number puzzle that plays like a mathematical crossword. The grid contains dark clue cells and white answer cells. Each clue cell is split diagonally — the number in the upper-right is the target sum for the white cells running to the right, and the number in the lower-left is the target sum for the cells running downward.

Your job is to fill every white cell with a digit from 1 to 9 so that each consecutive run of white cells adds up to its clue — with no digit repeated within the same run. Kakuro requires no guessing; every puzzle on this page has exactly one solution reachable through pure logical deduction.

How to Play Kakuro

  1. Read the clues. Dark cells show target sums. The upper-right number is the "across" clue (sum of the white cells to its right). The lower-left number is the "down" clue (sum of the cells below).
  2. Fill with 1–9. Place a single digit (1 through 9) in each white cell.
  3. Sum constraint. The digits in each horizontal or vertical run must add up exactly to the clue.
  4. No repeats. Within any single run, every digit must be unique — no using "3" twice in the same run, even if it would make the sum work.
  5. Cross-reference. Each white cell belongs to one horizontal run and one vertical run. Use the intersection of constraints to narrow down possibilities.

Kakuro Strategy Tips

1. Learn the Key Combinations

Certain run-length / sum pairs have only one valid combination of digits. For example: a 2-cell run summing to 3 must be {1, 2}; a 2-cell run summing to 4 must be {1, 3}; a 2-cell run summing to 17 must be {8, 9}. Memorise the forced combinations for 2-cell and 3-cell runs — they are the foundation of efficient Kakuro solving.

2. Start with the Most Constrained Runs

Look for the shortest runs (2–3 cells) and extreme sums (very low or very high). These have the fewest valid digit combinations and often let you place digits immediately. A 3-cell run summing to 6 can only be {1, 2, 3}; a 3-cell run summing to 24 can only be {7, 8, 9}.

3. Use Pencil Marks Extensively

Toggle Notes mode (📝) and mark all candidate digits in each cell. As you place digits elsewhere, come back and eliminate candidates. When a cell has only one candidate left, that's your answer.

4. Cross-Reference Intersecting Runs

Every cell sits at the intersection of a horizontal and vertical run. If the horizontal run limits a cell to {1, 3, 5} and the vertical run limits it to {3, 7}, the cell must be 3. This cross-referencing is the core technique in Kakuro.

5. Eliminate by Sum Remainder

If you've placed some digits in a run, subtract them from the clue to get the remaining sum. Then figure out which unused digits can form that remaining sum. This often eliminates candidates faster than checking each cell individually.

6. Watch for Hidden Singles

Sometimes a digit can only go in one cell within a run, even though that cell has other candidates. Scan each run: if digit 5 can only fit in one cell of the run, place it there — regardless of what the other run through that cell allows.

History of Kakuro

Kakuro traces its roots to Dell Magazines in the United States, where it first appeared in 1966 under the name "Cross Sums". The puzzle remained a niche favourite for decades until the Japanese publisher Nikoli popularised it in the 1980s, coining the name カックロ (Kakkuro) — a contraction of "addition cross" in Japanese.

Kakuro gained mainstream Western attention in 2005, riding the Sudoku wave. The Guardian and The Times began publishing daily Kakuro puzzles, and several books became bestsellers. Unlike Sudoku, Kakuro requires arithmetic in addition to logic, which gives it a distinctive character. Many puzzle enthusiasts consider Kakuro more challenging and rewarding than Sudoku because of the added numerical constraint.

Today Kakuro appears in newspapers, puzzle magazines, and apps worldwide. It is considered one of the "big three" Japanese logic puzzles alongside Sudoku and Nonograms.

Frequently Asked Questions

Kakuro is a logic-based number puzzle often described as a mathematical crossword. The board has dark clue cells and white cells you fill in. Each clue gives the sum for a consecutive run of white cells. You must fill each run with digits 1–9 that add up to the clue, with no digit repeated within the same run.
Sudoku requires placing digits 1–9 in rows, columns, and 3×3 boxes with no repeats. Kakuro also forbids repeats within a run, but adds an arithmetic constraint: the digits must sum to a specific clue value. Kakuro grids vary in shape and size, whereas Sudoku always uses a fixed 9×9 grid.
No. Every Kakuro puzzle on this site has a unique solution that can be reached through pure logic. Start with the most constrained runs — short runs or extreme sums (very low or very high) — because they have fewer valid digit combinations.
Look for "forced" combinations first. A 2-cell run summing to 3 must be {1,2}, and a 2-cell run summing to 17 must be {8,9}. Use pencil marks (the Notes mode) to track candidate digits, then cross-reference intersecting runs to narrow down possibilities.
Yes. This version is fully mobile-optimised with a tap-to-select interface and an on-screen number pad. The grid scales to fit your screen.
Each dark clue cell is split diagonally. The number in the upper-right tells you the sum for the white cells running to the right. The number in the lower-left tells you the sum for the white cells running downward. Some clue cells have both an across and a down clue.

More Puzzle & Strategy Games

If you enjoy Kakuro, try these other free games on our site:

Nonograms

Fill a grid using row-and-column number clues — also known as Picross or Griddlers.

Minesweeper

Classic mine-clearing logic. Uncover cells, read the numbers, flag the mines.