Techniques

How to Use Naked Pairs in Sudoku: A Simple Technique for Faster Solving

Tuesday, January 28, 2025

Introduction

If you've mastered Singles (Hidden & Naked), the next skill you should add is Naked Pairs — a clean, logical method for eliminating candidates and advancing stuck puzzles.

Naked Pairs commonly appear in Medium and Hard difficulty puzzles and often unlock major progress.

This guide explains what Naked Pairs are, how to identify them, and how to use them effectively. Understanding Naked Pairs is essential for progressing beyond basic techniques.

Key Points

Master these fundamentals to use Naked Pairs effectively:

  • Naked Pairs appear in rows/columns/boxes: They work in any unit
  • The pair "locks" two cells to exactly two candidates: Guaranteed placement
  • All other cells in the unit lose those numbers: Powerful elimination
  • A powerful candidate-cleaning technique: Removes clutter efficiently
  • Ideal for Medium → Hard puzzles: Essential for intermediate solving

What Is a Naked Pair?

A Naked Pair is a Sudoku solving technique where two cells in the same row, column, or box contain exactly the same two pencil-mark candidates. A Naked Pair happens when two cells in the same:

  • row
  • column
  • or box

contain exactly the same two pencil-mark candidates, such as {3, 7}.

Example:

. . . . . . . . .

. . {3,7} . . . . . {3,7}

. . . . . . . . .

You now know:

Those two cells MUST contain the numbers 3 and 7

Therefore, all other cells in that row/column/box cannot contain 3 or 7

This elimination often reveals new singles.

How It Works (Step-by-Step)

Using Naked Pairs requires systematic detection:

Step 1: Enable Notes Mode

You can't find Naked Pairs without pencil marks. Notes reveal candidate patterns clearly.

Step 2: Scan Each Row

Look for two cells with identical candidate sets. Check every row systematically for matching pairs.

Step 3: Scan Columns

Often easier because vertical alignment reveals patterns. Columns frequently show clear pair structures.

Step 4: Scan Each Box

Pairs frequently group inside 3×3 boxes. Box-level pairs are powerful and common.

Step 5: Apply Elimination

Remove both candidates from other cells in that unit. This creates immediate candidate reduction.

Step 6: Re-check Intersections

Pairs often cascade into new singles. After elimination, scan for new opportunities.

Where Naked Pairs Commonly Occur

In Rows: Two cells in one row share the same pair.

In Columns: The same pair appears in two cells along a column.

Inside Boxes: Pairs exist within a 3×3 box.

Hybrid Cases: A Naked Pair in a box may intersect with a row/column that contains overlapping candidates — this creates additional eliminations.

Why Naked Pairs Matter

Naked Pairs help:

  • reduce candidate clutter — clean up messy grids
  • reveal Hidden Singles — eliminations create immediate placements
  • prevent wrong guesses — logical certainty prevents errors
  • build momentum toward advanced techniques — foundation for progression
  • clean puzzle structures efficiently — fast candidate reduction

They're one of the fastest "candidate elimination" techniques.

Examples

Here are practical examples demonstrating Naked Pairs:

Example A — Row Naked Pair {2,8}

Row 4 has:

{2,8} . . . . . . {2,8} .

Eliminate all 2s and 8s from the other 7 cells.

Result: Candidate reduction reveals new solving opportunities.

Example B — Box Naked Pair {1,9}

Cells R2C2 and R1C3 in Box 1 have {1,9}. You must remove {1,9} from the remaining 7 box cells.

Result: Box-level elimination creates space for other numbers.

Example C — Naked Pairs Trigger Hidden Singles

After elimination, a cell becomes {6} → solve instantly.

Result: Pairs often cascade into immediate placements.

Common Mistakes

Mistake: Confusing Naked Pairs with Hidden Pairs

Naked Pair = same visible candidates

Hidden Pair = same hidden "required" numbers

Mistake: Ignoring boxes

Pairs inside boxes remove many candidates and are often overlooked.

Mistake: Checking only one direction

Always check rows, columns, and boxes.

Summary

Naked Pairs are a clean, efficient way to eliminate candidates and advance through Medium and Hard puzzles.

When combined with Locked Candidates, players unlock a major leap in solving ability. Mastering Naked Pairs is essential for intermediate Sudoku solving.

❓ FAQ

Q1: Is Naked Pair a beginner or intermediate technique?

Intermediate — it's often the next step after Singles. Essential for Medium+ puzzles.

Q2: Do Naked Pairs appear in every puzzle?

Almost all Medium or Hard puzzles include at least one. They're very common in intermediate puzzles.

Q3: Do I need to use Notes?

Yes, otherwise you can't spot pairs. Notes are essential for Naked Pair detection.

Q4: What's the difference between Naked Pairs and Hidden Pairs?

Naked: the candidates are visibly identical. Hidden: the candidates are the only two in a unit but may be hidden among others.

Q5: Does SudokuGames.org support notes?

Yes — and the grid spacing makes pairs easy to identify.

Q6: Can Naked Pairs solve puzzles alone?

Not usually, but they're essential for Medium/Hard progression. Combine with other techniques for complete solving.

Q7: How many Naked Pairs might appear in one puzzle?

Medium puzzles typically have 2-5 pairs. Hard puzzles may have more as candidate density increases.

Q8: Should I look for pairs first or singles?

Always fill Singles first, then scan for Pairs. This creates a logical solving flow.

Ready to master Naked Pairs? Start practicing with Notes Mode enabled today!

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