How to Play XV Sudoku

X between cells means they sum to 10; V means they sum to 5

Play XV Sudoku Free → XV Sudoku Puzzles

The Rules

Standard Sudoku rules apply: fill every row, column, and 3×3 box with the digits 1–9, each appearing exactly once.

XV Sudoku (also called Ten-Five Sudoku) places X and V markers between adjacent cells. An X means the two cells sum to 10; a V means they sum to 5. Many XV puzzles use the negative constraint: the absence of a marker guarantees the pair neither sums to 10 nor to 5. Combined with standard Sudoku, this provides very tight constraints across the grid.

At a Glance

18–24
Typical givens
Cell Relationships
Constraint type
~8m
Easy solve time
~18m
Medium solve time

How to Solve XV Sudoku

Beginner
Negative Constraint
Where no X or V appears between adjacent cells, their sum is neither 10 nor 5. This eliminates (1,9), (2,8), (3,7), (4,6) for X and (1,4), (2,3) for V.
Beginner
Sum Pair Enumeration
List all digit pairs that sum to 10 (for X) or 5 (for V), then use row/column placement to identify which pair must occupy each marked pair.
Intermediate
Marker Chain Logic
Multiple consecutive X and V markers in a row form a sum chain — enumerate valid assignments for the entire chain simultaneously.
Advanced
Box X-Interaction
An X pair forces both digits into specific positions within their shared box, constraining all remaining cells of that box.
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Common Questions

What digit pairs sum to 10? ▾

Only (1,9), (2,8), (3,7), and (4,6). The digit 5 cannot appear in an X pair.

What digit pairs sum to 5? ▾

Only (1,4) and (2,3). The digit 5 cannot be in any V pair within the 1–9 range.

Is the negative constraint always applied? ▾

Yes — our XV Sudoku uses the negative constraint: no X or V means neither condition holds.

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