Medium Odd/Even Sudoku

Shaded cells must hold odd digits; unshaded cells hold even digits. Parity clues cut candidates in half and make every placement count. Free online.

Easy Medium Hard Expert

Odd/Even Sudoku at medium difficulty. Parity-driven naked pairs and counting odd vs even cells in each row unlock placements that standard scanning misses.

5
7
8
1
2
9
3
6
9
5
2
3
7
4
6
5
9
8
6
5
8
6
5
9
1
7
1
7
1
8
2
2
Mistakes
0/3
Score
-
Time
00:00
Try Hard Odd-Even Sudoku →
Progress0%
Odd Even

What is Odd / Even Sudoku?

Difficulty
★★★☆☆
3/5
Constraint Type
Cell Relationships
Typical Givens
20–26
Avg. Solve (Medium)
14 min

Solving Techniques for Medium Level

Technique Description Level
Immediate Candidate Halving Marked cells instantly reduce to 5 odd candidates (1,3,5,7,9) or 4 even candidates (2,4,6,8). Apply this before any other technique. Beginner
Parity Counting per Box Count how many odd-marked and even-marked cells are in each box to verify the digit distribution is achievable. Intermediate
Parity-Chain Elimination If a row must contain exactly four even digits, and three positions are already even-marked, the fourth must come from the remaining unmarked cells. Intermediate

Master these, then take on Hard Odd / Even Sudoku to learn Advanced techniques.

Techniques to Master at Medium

  • Hidden Singles technique — Count parity per unit: if a row has one odd-marked cell left and one odd digit unplaced, the shading has handed you a hidden single.
  • Obvious Pairs technique — Parity pairs are easy to spot — two even cells in a box reduced to {2,8} lock both digits away from every other even-marked cell in that box.

Average Solve Time by Difficulty

Easy
6 min
Medium
14 min
Hard
28 min
Expert
50 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Odd / Even Sudoku →

Related Variants

Greater Than Sudoku

Builds on value reasoning — inequality chains bound cells from both ends much like parity halves them.

Kropki Sudoku

Moves from cell properties to cell relationships: dots encode consecutive and doubled neighbours.

Consecutive Sudoku

Neighbour-difference logic with a strong negative constraint — a natural next step from parity counting.

Frequently Asked Questions — Medium Odd/Even Sudoku

What techniques are most useful for medium Odd/Even Sudoku?
Medium puzzles reward combining parity logic with hidden singles. After applying parity restrictions, look at each row, column, and box for digits that can only go in one cell. Also watch for parity-driven naked pairs: if two cells in a box are both odd and their combined odd-digit candidates are restricted to the same two values, they form a naked pair.
How do parity constraints create naked pairs?
If two cells in a row are both odd-marked and the row already contains three of the five odd digits, those two cells can only hold the remaining two odd digits — forming an automatic naked pair. This eliminates those two digits from all other cells in the row, even unshaded ones. Parity-driven naked pairs appear frequently at medium difficulty.
How does the 5-odd vs 4-even asymmetry affect medium puzzles?
In every row and column there must be exactly five odd-valued cells and four even-valued cells (since 1–9 contains five odds and four evens). If a row already has many odd or even cells filled in, you know the parity composition of the remaining cells. This counting technique helps at medium level when direct scanning stalls.
Can I use parity to find hidden singles?
Yes. If a box has only one odd-marked cell remaining, and the odd digit that must go in that box (deduced from the rest of the box) is an odd number, it must go in that one odd-marked cell. This is a parity-forced hidden single and it is the most common breakthrough technique at medium difficulty.
How long does a medium Odd/Even Sudoku take?
Most players finish medium Odd/Even Sudoku in 15–25 minutes. Parity constraints provide so much early information that medium puzzles often feel faster than standard Sudoku at the same difficulty. The key is applying parity eliminations immediately and not treating unshaded cells as the only constraints.

More questions? See the full Odd/Even Sudoku guide.