Play Calcudoku (Keen) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Calcudoku combines a Latin square with arithmetic: every row and column holds each number once, and outlined cages show a target and an operation (add, subtract, multiply or divide) their digits must produce. It is widely published under the name KenKen. The puzzle is ready below; click a square and type a digit to begin.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Select a square | Arrow keys | Left-click |
| Enter a digit | Type the digit | Click, then type |
| Pencil marks | Enter toggles pencil mode, then type | Right-click, then type |
| Clear a square | Space | Click, then Space |
| Fill every empty square with all pencil marks | M | — |
| Undo / redo | U / R (or Ctrl+Z / Ctrl+R) | Game menu buttons |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Keen is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
On an N×N grid, fill each square with a digit from 1 to N so that:
- each digit appears once in every row and once in every column;
- the digits in each cage, combined with the cage's operation, give its target number.
A + cage is a sum and a × cage is a product. A − or ÷ cage always covers two squares; the larger digit minus (or divided by) the smaller gives the target, in either order. A digit may repeat inside a cage, as long as the repeats are not in the same row or column.
Sizes and difficulty
Presets run from 4×4 Easy up to 9×9 Normal, with 6×6 offered at Easy, Normal, Hard, Extreme and Unreasonable. Unreasonable may need trial and error; the levels below it can all be solved by reasoning alone. Some presets are "multiplication only", where every cage is a product (a variant sometimes called Inshi no Heya).
Solving tips
Fill single-square cages first: their target is the digit. Two-square cages with large products narrow quickly, so 12× on a 4×4 grid must be 3 and 4. Use the row and column totals: every row of an N×N grid adds up to the same amount, so a nearly complete row can tell you what a straddling cage must contribute. Pencil in candidates (M fills them all) and strike out those that clash with a row or column.
Where this puzzle comes from
Keen is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
Can a number repeat inside a cage?
Yes, provided the repeated digits are not in the same row or column. This is the opposite of Killer Sudoku, where cage digits must all differ.
How large can the grid be?
From 3×3 to 9×9; the limit is 9 because each square holds a single digit.
Is Calcudoku free to play here?
Yes, with no limit on the number of puzzles. Keen is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
More you can play in your browser
Related guides
- Sudoku (Solo)Play Sudoku free in your browser: endless generated puzzles from Trivial to Unreasonable,
- Futoshiki (Unequal)Play Futoshiki free in your browser: fill a Latin square that obeys every greater-than sig
- Skyscrapers (Towers)Play Skyscrapers free in your browser: place towers of every height once per row and colum
- DominosaPlay Dominosa free in your browser: find where each domino of a full set lies in a grid of
Want a game like this on your own site?
Calcudoku (Keen) isn't ours to give away — we host it, we didn't write it. But eleven of the games here we did write from scratch, and those are free for anyone to put on their own page: one line of HTML, no account, no permission, no attribution beyond a credit line.