Calcudoku Strategy: 6 Techniques

Every Calcudoku can be solved by writing down what each cage allows and crossing off what the rows and columns forbid. These six techniques do that in the right order. New here? Read the rules first.

1. Single cells first

A cage with no sign is a given digit. Fill it, then cross that digit out of its row and column.

2. Forced cages

Some cages have only one combination. In a 4×4, a 7+ two-cell cage must be 3 and 4; a 12× cage must be 3 and 4 too; a 3÷ cage must be 1 and 3. Write both candidates in both cells.

3. List the combinations

For every other cage, note the possible digit sets. A 6+ cage of two cells in a 5×5 is 5 or 4; a 2− cage is 3, 4 or 5. Small lists are where the puzzle cracks.

4. Big products, small differences

A × cage with a large target has few factorisations: 20× in a 5×5 is 5 or 5. A 1− cage with a 6 nearby must contain a 5. Extreme targets are the strongest clues.

5. Count the rows and columns

Each row adds up to 1 + 2 + … + N. If every cage but one in a row lies entirely inside it, the leftover cell's digit is the row total minus the cage targets, a trick that works for + cages and for single cells.

6. Pair the candidates

When two cells in a row can only be the same two digits, no other cell in that row can hold them. Combined with the cage lists, this usually finishes the grid without guessing.

Last updated 2026-10-20