Math Doku — Free Calcudoku-Style Math Logic Puzzle

Math Doku is a free Calcudoku-style logic puzzle that mixes Sudoku rules with arithmetic. Fill the grid so every row and column contains each number once, and make the numbers inside every outlined cage produce the cage’s target with +, −, × or ÷. Choose a 3×3 to 7×7 grid and Easy, Medium or Hard. No account is needed.

How to play Math Doku

1. Pick a grid size (3×3, 4×4, 5×5, 6×6 or 7×7) and a difficulty, then press New Puzzle. Press Today’s puzzle instead to play the daily puzzle for that size and difficulty. It is the same puzzle for everyone on the same calendar day.
2. Select a cell, then tap a number on the keypad or type it. On a 5×5 grid you use the numbers 1 to 5, on a 6×6 grid 1 to 6, and so on.
3. Every row and every column must contain each number exactly once. If you repeat a number in a row or column, both cells turn red.
4. The thick borders split the grid into cages. The numbers in a cage must combine to the label in its top-left corner.
5. When every cell is filled correctly, the board lights up and you get a results screen with your time and 1 to 3 stars.

New to this kind of puzzle? Press Quick tutorial for a guided 3×3 puzzle. It walks you through nine moves and explains the reason for each one.

Reading the cages

• A single number (for example 3) marks a one-cell cage. Just write that number in.
• 7+ means the cage’s numbers add up to 7.
• 12× means the cage’s numbers multiply to 12.
• 2− is always a two-cell cage: the larger number minus the smaller number equals 2, in either order.
• 3÷ is also a two-cell cage: the larger number divided by the smaller number equals 3.

Numbers may repeat inside a cage, but only when the repeated cells are in different rows and columns. When a cage is complete and its numbers make the target, its cells turn green. If a filled cage misses its target, the label turns red. A green cage still has to fit its rows and columns, so use Check if you are unsure.

Easy puzzles use only + and −. Medium adds ×. Hard uses all four operations with more three- and four-cell cages. Every puzzle is generated fresh and checked by a solver so it has exactly one solution, which means it can always be solved with logic, without guessing.

Solving strategies

• Start with one-cell cages. They are free numbers.
• Look for cages with only one possible pair. In a 4×4 grid, a two-cell 12× cage must be 3 and 4, and a 7+ cage must also be 3 and 4. In a 6×6 grid, 11+ can only be 5 and 6.
• Use the extremes. A large product such as 60× or a large sum needs the biggest numbers. A 1− cage means the two numbers are next to each other, like 3 and 4.
• Count what each row needs. Every row adds up to the same total (10 in a 4×4, 15 in a 5×5, 21 in a 6×6). If you know all but one cell of a row, subtraction gives you the last one.
• Combine clues. When a cage’s possible pair and a row’s missing numbers overlap in only one way, you have found a cell.

Notes, hints and settings

• Notes: switch to Notes mode (or press N) to pencil in small candidate numbers. You can also hold Shift while typing a number. When you place a number, that number is removed from the notes in the same row and column.
• Auto-notes fills every empty cell with all the numbers that still fit its row, column and cage. You then cross them off.
• Undo, Redo, Erase and Restart let you change your mind. Restart clears the board but keeps the timer running.
• Check flashes any filled cell that is wrong. Hint fills one correct cell: the selected cell if it is empty or wrong, otherwise the empty cell with the fewest possibilities. Ollie explains how the hint fits its cage.
• Reveal shows the whole solution and ends the puzzle without stars.
• Keyboard: arrow keys move, number keys fill, Backspace erases, Ctrl+Z undoes and Ctrl+Y redoes.

Stars: 3 stars for a solve with no hints and no wrong checks, 2 stars with up to two hints, and 1 star with more help. The game keeps your best time for each size and difficulty on this device. You also earn stickers, such as Daily Solver and Hard Hero, and XP that counts toward your Effortless Math player level.

What Math Doku teaches

Each cage is a small “find the missing numbers” problem. Solving it builds fact fluency with addition, subtraction, multiplication and division, and practice with factor pairs and inverse operations. The row and column rule adds logical reasoning: you eliminate possibilities, test cases and justify each step. These are the same habits that help with algebra and with multi-step test questions. A 4×4 Easy puzzle works well for upper elementary students. 6×6 and 7×7 Hard puzzles challenge middle school students and adults.

FAQ

Is this the same as KenKen? It follows the same well-known Calcudoku-style rules. KenKen is a trademark of KenKen Puzzle LLC, and Math Doku is Effortless Math’s own free version.

Can a number repeat in a cage? Yes, if the repeated cells are not in the same row or column.

Does the order matter for − and ÷? No. The label describes the larger number minus or divided by the smaller one.

Is my progress saved? Your best times, stickers and level are saved in this browser on this device. They are not linked to an account.