Easy Diagonal Sudoku

Both main diagonals must also contain 1–9 without repetition. Four units instead of three — twice the constraint density.

Easy Medium Hard Expert

New to Diagonal Sudoku? Both highlighted diagonals must contain 1–9 exactly once — the center cell sits on both, making it the most constrained cell on the board. Start here.

4
2
5
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8
5
4
1
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9
9
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6
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1
7
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1
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9
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4
2
7
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3
5
1
Mistakes
0/3
Score
-
Time
00:00
Try Medium Diagonal Sudoku →
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What is Diagonal Sudoku?

Difficulty
★★☆☆☆
2/5
Constraint Type
Extra Regions
Typical Givens
22–28
Avg. Solve (Easy)
4 min

Solving Techniques for Easy Level

Technique Description Level
Diagonal as a Unit Treat each diagonal exactly like a row or column — every digit 1–9 appears exactly once. Standard scanning and counting apply. Beginner

Ready to go deeper? Try Medium Diagonal Sudoku to unlock Intermediate techniques.

Techniques to Master at Easy

  • Last Free Cell technique — Rows that cross a diagonal empty out faster here — when hunting the final gap in a unit, remember the two diagonals count as units too.
  • Last Possible Number technique — Diagonal cells are checked against four houses instead of three, so elimination often leaves a single candidate on the very first pass.
  • Notes in Sudoku — When pencil-marking, strike candidates from a cell's diagonal as well as its row, column, and box — the 17 diagonal cells start with visibly shorter lists.

Average Solve Time by Difficulty

Easy
4 min
Medium
10 min
Hard
20 min
Expert
40 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Diagonal Sudoku →

Related Variants

Irregular Diagonal Sudoku

Keeps both diagonal houses you've learned to scan and adds jigsaw regions for an even denser constraint web.

Hyper Sudoku

The same extra-region idea — four shaded windows instead of two diagonals — so your habit of scanning bonus houses transfers directly.

Jigsaw Sudoku

If you enjoy adapting your scan to new house shapes, jigsaw regions stretch that skill further than straight diagonal lines.

Frequently Asked Questions — Easy Diagonal Sudoku

What is Diagonal Sudoku?
Diagonal Sudoku is a variant that adds two extra constraints: both main diagonals of the 9×9 grid must each contain the digits 1–9 exactly once. The main diagonal runs from the top-left to the bottom-right corner, and the anti-diagonal runs from the top-right to the bottom-left corner.
Which cells are on the diagonals in Diagonal Sudoku?
The main diagonal (↘) passes through cells (1,1), (2,2), (3,3) … (9,9). The anti-diagonal (↙) passes through (1,9), (2,8), (3,7) … (9,1). The center cell (5,5) sits on both diagonals, making it the most constrained cell on the board.
Does Diagonal Sudoku still follow standard Sudoku rules?
Yes. Every row, every column, and every 3×3 box must still contain the digits 1–9 exactly once. The diagonal rule is an additional constraint, not a replacement for these standard rules.
How do I start solving an easy Diagonal Sudoku?
Begin with the center cell (row 5, column 5) — it belongs to both diagonals, both standard diagonals from its box, a row, and a column. With five constraints it is usually the most restricted cell. Then work outward along the diagonals using the same elimination logic as rows and columns.
How many extra constraints do the diagonals add?
The two diagonals add 2 extra uniqueness groups, giving a total of 29 constraint groups (9 rows + 9 columns + 9 boxes + 2 diagonals). This additional structure typically makes Diagonal Sudoku easier to solve than regular Sudoku with the same number of given digits.

More questions? See the full Diagonal Sudoku guide.