Making a puzzle…
How to play Calcudoku
Calcudoku is a number logic puzzle that mixes a Latin square with a little arithmetic. Fill the grid so that no number repeats in any row or column, and so that the numbers in each outlined group of cells, called a cage, make the target shown in its corner.
The rules
- A board of size N uses the numbers 1 to N. A 6×6 board uses 1 to 6.
- Each row holds every number once. Each column holds every number once.
- Each cage shows a target and an operation. The numbers in the cage must give the target with that operation:
- + adds them all: a cage of 2, 3 and 4 makes 9+.
- × multiplies them all: 2, 3 and 4 make 24×.
- − takes the smaller from the larger. It only appears in cages of two cells: 6 and 2 make 4−.
- ÷ divides the larger by the smaller. It also only appears in cages of two cells: 6 and 2 make 3÷.
- A cage of one cell shows just a number. That number goes in the cell.
- A number may repeat inside a cage, as long as the two cells are not in the same row or column.
Every puzzle here has exactly one solution, and you can reach it by reasoning alone. Our solver checks each board before you see it.
Buttons
- Pick a cell, then press a number below the board, or type it.
- Notes turns on pencil marks: numbers you press go into the cell as small reminders. Press Notes again to go back to writing answers.
- Erase clears the picked cell. Undo takes back your last move.
- Hint fills in one cell that follows from what is on the board and says why. If a number you wrote is wrong, it points to that first.
- Pause hides the board and stops the clock.
- Check against the answer marks numbers that are not in the solution as soon as you write them. It is off by default; rule breaks (a number twice in a row, a cage that misses its target) are always marked.
On a keyboard: arrow keys move, 1–9 write, Backspace erases, N switches notes, Ctrl+Z (⌘Z) undoes.
Sizes
| Size | Numbers | Good for |
|---|---|---|
| 4×4 | 1–4 | Learning the rules |
| 5×5 | 1–5 | A short break |
| 6×6 | 1–6 | The everyday puzzle |
| 7×7 | 1–7 | A longer think |
| 8×8 | 1–8 | Practised players |
| 9×9 | 1–9 | The full challenge |
Tips
- Start with one-cell cages. Their number is given: write it in.
- List what a cage can be. In a 4×4 board, a two-cell 3− cage can only be 1 and 4. A 12× cage in a 6×6 board can be 2·6 or 3·4.
- Use the rows and columns. Once a number is placed, it can’t appear again in its row or column. Notes help you keep track.
- Look for a number with one place left. If 5 fits in only one cell of a row, it goes there.
- Add up a whole row. Every row of a 6×6 board adds up to 21 (1+2+3+4+5+6). If you know most of a row, the rest follows.
Questions
Is Calcudoku the same as KenKen?
Calcudoku is the same kind of puzzle that is sold under the KenKen® brand. KenKen is a registered trademark of its owners. Numberdoku is an independent site and is not connected with them.
Why do numbers repeat inside a cage?
The only rule for repeats is the row and column rule. Two cells of an L-shaped cage that sit in different rows and columns may hold the same number.
Is my progress saved?
Yes. Your game for each size is saved in this browser, so you can close the page and come back. Nothing is sent to us.