Arrow keys to navigate · P to toggle notes · Ctrl+Z to undo
How to Play KenKen
Choose Your Settings
Click 'New Game' to open the settings panel. Select a grid size (3×3 is the gentlest introduction; 6×6 is a satisfying challenge). Choose Easy, Medium, or Hard difficulty — this affects how large and complex the cages are. Pick an operation mode: 'Add Only' is great for beginners or younger players; 'All (+−×÷)' is the classic full experience. Then click 'Start New Game'.
Read the Cage Labels
Each cage has a small label in its top-left cell showing a target number and operation (e.g., '12+', '3−', '6×', '2÷'). Single-cell cages show only a number — place that digit there immediately. For multi-cell cages, figure out which digit combinations satisfy the arithmetic target while also obeying the no-repeat-in-row/column rule.
Fill the Grid
Click a cell to select it, then press a number key (1–N) or tap a number on the on-screen pad. Red highlighting appears automatically if you place a digit that conflicts with another in the same row or column — fix it immediately. Use Notes mode (press P or click the Notes button) to write candidate digits as small pencil marks inside cells. When all cells in a cage are correctly filled, the cage turns lightly highlighted to confirm it.
Use the Tools When Stuck
Press Ctrl+Z or click Undo to reverse your last move (unlimited undo history). Click Hint to auto-fill one correct cell when you are completely stuck. Click Check to reveal any incorrect cells in red. Use Reset to clear all your entries and start the same puzzle from scratch. Your progress saves automatically — close the tab and come back anytime to resume exactly where you left off.
Frequently Asked Questions
What is the difference between KenKen, Calcudoku, and MathDoku?
They are essentially the same puzzle under different brand names. KenKen is the original trademark name registered by Tetsuya Miyamoto and popularized by Nextoy LLC in the West. Calcudoku and MathDoku are generic names used by independent puzzle sites to offer the same type of puzzle without trademark issues. Kendoku is another variant name. The rules are identical across all versions: fill an NxN grid so no digit repeats in any row or column, and every cage's digits produce the stated arithmetic result. Some sites introduce minor rule variations — for example offering 'no-op' mode where the operation symbol is hidden — but the fundamental puzzle is the same invention.
Can digits repeat inside a cage?
Yes — digits CAN repeat within a cage, as long as they do not share a row or column. This is a common point of confusion for players coming from Sudoku, where no repetition of any kind is allowed within a box. In KenKen, the only hard rule is that no digit may appear twice in the same row or twice in the same column across the entire grid. So two cells in the same cage can both hold the digit 2 if those cells are in different rows AND different columns. For example, a '4+' cage in a 4×4 grid could contain {2,2} if the two 2s occupy different rows and different columns.
Why are subtraction and division limited to two-cell cages?
Subtraction and division are not associative operations: the result of (a − b) − c depends on the order of operations and is not the same as a − (b + c). For three or more cells there would be many different valid interpretations of how to apply the operation, making the puzzle ambiguous. By restricting subtraction and division to exactly two-cell cages, each cage has a single unambiguous arithmetic relationship: |a − b| = target for subtraction, and max(a,b) ÷ min(a,b) = target for division, regardless of which order the digits appear in the cells.
How do I use pencil marks effectively?
Toggle Notes mode by pressing P or clicking the Notes button — the button turns highlighted when active. In notes mode, pressing a digit adds it as a small candidate mark inside the selected cell rather than placing it as the definitive answer. Build up the set of possible digits for each cell based on cage constraints and which digits already appear in the cell's row and column. When only one candidate remains in a cell, that is the answer — press the digit again in normal mode to place it. Our game automatically removes pencil marks from the same row and column when you place a confirmed digit, saving you maintenance work.
What does the difficulty setting change?
Difficulty primarily affects cage size and structure. Easy puzzles have more single-cell cages (free given digits) and smaller multi-cell cages (2–3 cells), which are more constrained and easier to deduce. Medium puzzles have fewer givens and allow cages up to 4 cells, increasing the number of candidate combinations you need to consider. Hard puzzles have larger cages (up to 5 cells), fewer single-cell hints, and more reliance on multiplication and division in modes that include those operations, requiring more advanced constraint propagation. Grid size also contributes to difficulty: a 6×6 Hard puzzle is significantly more challenging than a 3×3 Easy.
Is my game saved if I close the browser?
Yes. The game automatically saves your current board state, timer, notes, and all your moves to your browser's local storage every time you make a change. When you return to the page it will load your in-progress puzzle exactly as you left it, including your pencil marks and elapsed time. Your save is device-specific and browser-specific — it will not transfer to another device or browser. If you clear your browser data or use private/incognito mode the save will be lost. Completing a puzzle or starting a new game will replace the saved state with the new game.