9×9 · Easy to hard
Even-Odd Sudoku
Classic sudoku with a constraint on which cells hold even or odd digits.
Medium00:00
What is even-odd sudoku?
Even-odd sudoku marks some cells in a way that fixes the parity of their digit. Shaded cells must hold even digits (2, 4, 6, 8); unshaded cells must hold odd (1, 3, 5, 7, 9). Standard sudoku rules apply to the digits themselves.
Rules
- Standard 9×9 sudoku rules apply: digits 1–9 once per row, column, and 3×3 box.
- Shaded cells must contain an even digit (2, 4, 6, or 8).
- Unshaded cells must contain an odd digit (1, 3, 5, 7, or 9).
Tips
- Even digits are rarer (only four of them per row), so shaded cells are heavily constrained. start there.
- When scanning for a specific digit, immediately eliminate cells of the wrong parity.
- Often more accessible than other variants because the parity constraint guides early moves.
Related variants
- Consecutive Sudoku, Classic sudoku with markers showing which adjacent cells differ by exactly one.
- Diagonal Sudoku (X-Sudoku), Classic sudoku plus a constraint on both main diagonals.
- Killer Sudoku, Sudoku meets killer-style arithmetic: every dotted region sums to its total.
- Classic sudoku for comparison
Even-Odd Sudoku FAQ
Does the shading change the digit constraints?
No. The standard 1–9 row/column/box rules still apply. Shading only restricts which parity of digit can go in a cell.
Are there always exactly four evens per row?
Yes. There are four even digits (2, 4, 6, 8), and each appears exactly once per row.
Is even-odd easier than classic?
At the same clue count, even-odd is easier because the parity hint reduces candidate sets immediately.
Are puzzles unique?
Yes. Uniqueness is verified.
Can the engine highlight parity errors?
Yes. when you enter a wrong-parity digit in a shaded or unshaded cell, the cell will flag the conflict.