Odd / Even Sudoku
Shaded cells must contain odd digits; circles must contain even digits
Odd / Even Sudoku is fully playable. Choose a difficulty and start solving.
Marked cells commit to a parity before you know the digit: odd markers allow 1, 3, 5, 7 or 9, even markers allow 2, 4, 6 or 8. Counting how many odd and even slots remain in each unit becomes a solving tool of its own. A comfortable mid-tier variant — more bookkeeping than the classic game, with no arithmetic.
For the complete rules, worked examples and solving techniques, read the full How to Play Odd / Even Sudoku guide.
Like all Sudoku variants, Odd / Even Sudoku builds on the classic 9×9 foundation. Every row, column, and 3×3 box must contain each digit from 1 to 9 exactly once. The variant constraint is added on top of these standard rules, never replacing them.
If you're new to Sudoku, start by learning the basic rules and techniques before attempting variants.
Techniques Useful for This Variant
| Technique | How it applies |
|---|---|
| Pencil Marks / Notes | Essential for tracking candidates alongside the variant constraint |
| Obvious Singles | Cells narrowed to one candidate by the combined constraints |
| Hidden Singles | Digits with only one valid cell in a unit after variant elimination |
| Pairs and Triples | Locked candidates exposed by the additional constraint |