Sudoku Candidate Strategy
Naked Pair Sudoku Technique: Step-by-Step Guide
Learn how to find Naked Pairs in rows, columns, and 3×3 boxes, eliminate candidates correctly, and use this technique to solve harder Sudoku puzzles.
Two Cells, Two Candidates
When two cells in one unit contain exactly the same two candidates, those candidates are locked into the pair.
Use Accurate Notes
Naked Pairs are visible only when candidate notes are complete and current.
Match Two Cells
Look for two cells in the same unit that contain exactly the same two candidates.
Remove From Others
Remove the pair candidates only from other cells in that same row, column, or box.
What Is a Naked Pair in Sudoku?
A Naked Pair occurs when two unsolved cells in the same row, column, or 3×3 box contain exactly the same two candidates.
For example, if two cells in one row both contain only {3,8}, one cell must become 3 and the other must become 8. You may not know which is which yet, but those numbers are reserved for those two cells.
Because 3 and 8 must occupy the pair, they can be removed from every other unsolved cell in that same row.
Why Is It Called a Naked Pair?
The pair is called “naked” because the two candidates are clearly visible as the only candidates in those two cells.
Simple Example
Cell A = {2,7}
Cell B = {2,7}
If both cells share a row, column, or box, remove 2 and 7 from the other cells in that unit.
How to Find a Naked Pair
Choose One Unit
Check one row, column, or 3×3 box at a time.
Look for Bivalue Cells
A bivalue cell contains exactly two candidates. Compare it with other bivalue cells in the same unit.
Confirm the Candidates Match
Both cells must contain exactly the same two candidates, such as {4,9} and {4,9}.
Remove the Pair From Other Cells
Remove those two candidates from every other unsolved cell in the same unit. Keep them in the pair cells.
Rescan for New Singles
After eliminating candidates, check whether another cell now has only one possible number.
Naked Pair in a Row
Suppose row 5 contains two cells with candidates {1,6}. No other candidates appear in those cells.
Row Example
Remove 1 and 6 from R5C9. It becomes {3,8}.
Naked Pair in a Column
A column-based Naked Pair works exactly the same way. The two matching cells must share one column.
Column Example
If R2C4 and R8C4 both contain only {3,5}, remove candidates 3 and 5 from all other unsolved cells in column 4.
The pair does not need to sit next to each other. It only needs to be in the same column.
Naked Pair in a 3×3 Box
If two cells in one box contain exactly the same two candidates, those candidates can be removed from the other cells in that box.
Box Example
If two cells in the top-left box contain only {4,9}, remove 4 and 9 from every other unsolved cell in that box.
If the two pair cells also share a row or column, the pair may create additional eliminations in that line.
Why the Naked Pair Elimination Is Valid
If two cells in one unit are limited to the same two candidates, those two candidates must fill those cells in some order.
Option A
First cell = 2
Second cell = 8
Option B
First cell = 8
Second cell = 2
Either way, 2 and 8 are reserved for those two cells, so no other cell in the unit can contain 2 or 8.
When Should You Look for a Naked Pair?
After Singles Stop
Search for Naked Pairs when naked singles and hidden singles no longer produce progress.
When Many Cells Have Two Candidates
A unit with several bivalue cells is a good place to compare candidate pairs.
In Medium and Hard Puzzles
Naked Pairs are common in Medium and Hard Sudoku and can also appear in Expert puzzles.
When Candidate Lists Are Crowded
A Naked Pair can simplify a unit by removing two candidates from several other cells.
When Is It Not a Naked Pair?
❌ The Cells Do Not Share a Unit
Two matching cells do not form a Naked Pair unless they share the same row, column, or box.
❌ One Cell Has Extra Candidates
Cells {2,7} and {2,7,9} are not a Naked Pair.
❌ The Candidate Sets Differ
Cells {1,4} and {1,6} are not a Naked Pair.
❌ Three Cells Share the Same Pair
If three cells all contain only {3,8}, recheck the candidate notes because this is not a valid two-cell pair.
Common Naked Pair Mistakes
❌ Removing Outside the Unit
A row pair eliminates only in that row. A column pair eliminates only in that column.
❌ Removing From the Pair Cells
Keep both candidates in the pair until another logical step decides which is which.
❌ Using Incomplete Notes
A missing candidate can make a false pair appear.
❌ Expecting an Immediate Placement
Naked Pairs often create eliminations rather than direct answers.
Naked Pair vs. Hidden Pair
Naked Pairs restrict cells. Hidden Pairs restrict candidate positions.
Naked Pair vs. Locked Candidates
Naked Pair vs. Naked Triple
How to Practise Naked Pairs
1. Turn On Notes
Fill in candidate notes for every unsolved cell.
2. Scan Bivalue Cells First
Cells with exactly two candidates are the easiest places to begin.
3. Compare Within One Unit
Compare pairs only within one row, one column, or one box at a time.
4. Explain Every Elimination
Identify the pair cells, pair candidates, and shared unit before removing anything.
Naked Pair Practice Checklist
- 1. Are both cells in the same row, column, or box?
- 2. Does each cell contain exactly two candidates?
- 3. Are the candidate sets identical?
- 4. Are the notes complete and current?
- 5. Are you removing candidates only from other cells in the unit?
- 6. Did you rescan for singles afterward?
Related Sudoku Learning Pages
🧠 Advanced Sudoku Techniques
Learn subsets, fish patterns, wings, coloring, unique rectangles, and chains.
✖️ X-Wing Sudoku
Learn the four-corner pattern used to remove candidates across rows and columns.
📘 Sudoku Strategies
Review essential solving methods before moving to harder techniques.
🟠 Hard Sudoku
Practise candidate elimination and Naked Pair recognition.
Frequently Asked Questions
What is a Naked Pair in Sudoku?
A Naked Pair is formed when two cells in the same row, column, or box contain exactly the same two candidates.
Why is it called a Naked Pair?
The two candidates are visible as the only candidates in the pair cells.
Can a Naked Pair appear in a 3×3 box?
Yes. Naked Pairs can appear in rows, columns, and 3×3 boxes.
Does a Naked Pair place a number directly?
Usually not. It removes candidates from other cells and may reveal a single afterward.
What is the difference between Naked Pair and Hidden Pair?
A Naked Pair is found by identifying two cells containing only the same two candidates. A Hidden Pair is found by identifying two candidates that appear only in the same two cells.
Practise Finding Naked Pairs
Open a Medium or Hard Sudoku puzzle, turn on Notes, and compare bivalue cells inside each row, column, and box.