Calcudoku
Calcudoku is an arithmetic logic puzzle on a square grid. Fill each row and column with the digits from 1 up to the grid's size, once each. Thick outlines group cells into cages, and each cage's digits must make the number in its corner using the operation shown: add, subtract, multiply or divide.
How to play
Every Calcudoku here has exactly one solution and can be solved by logic alone. The grid grows from 4×4 at Easy to 6×6, and the level is set by the hardest technique the puzzle needs.
- Each row and each column holds every digit from 1 to the grid size once.
- A cage's digits make its number with its operation: + adds, × multiplies.
- − and ÷ cages have two cells and work in either order, larger digit first.
- A one-cell cage simply shows its digit; digits may repeat within a cage if they are in different rows and columns.
Playing on this site
- Select a cell, then type a digit or tap it on the number pad. Arrow keys move the selection.
- Turn on Notes (or press N) to pencil in candidates instead of answers.
- Hint first points out any wrong digits, then names the next technique and shows where it applies before giving anything away.
- Your puzzle is saved in this browser, so you can come back to it later.
Techniques by level
Every technique the solver knows, from easiest to hardest. A puzzle's level is the hardest one it needs.
Easy
- Hidden single
- In the highlighted row or column this digit fits in only one cell.
- Cage arithmetic
- Only some digits can make this cage's number with its sign, so the marked candidates are out.
Medium
- Naked pair
- Two cells share the same two candidates, so those digits leave the rest of their area.
- Hidden pair
- Two digits fit only in the same two cells, so those cells hold nothing else.
- Cage and line
- Every way to fill this cage uses a digit whose places in the cage share one line, so the rest of that line can't have it.
Hard
- Naked triple
- Three cells hold only three digits between them, so those digits leave the rest of their area.
- Hidden triple
- Three digits fit only in the same three cells, so those cells hold nothing else.
- X-Wing
- A digit is limited to the same two columns in two rows (or the reverse), so it leaves the rest of those lines.
Expert
- Contradiction
- Try another digit in the marked cell and a rule breaks a few steps later. So that digit is out.
Questions
Can a digit repeat inside a cage?
Yes, as long as the two cells are in different rows and different columns. The only rule for a row or column is that each digit appears once.
Will I ever have to guess?
No. Every puzzle has exactly one solution that logic alone reaches, at every level.
Is Calcudoku free to play here?
Yes. Every level is free, with no account and no sign-in.