Naked Pairs in Sudoku: How to Spot Them Instantly
If there's one technique that separates casual sudoku players from serious solvers, it's the naked pair. It's not flashy like the X-Wing or intimidating like the Swordfish. But it's the technique you'll use most often, and learning it will immediately level up your game.
What Is a Naked Pair?
A naked pair is two cells in the same row, column, or 3x3 box that contain exactly the same two candidates — and nothing else.
Example: Cell A has candidates {4, 7}. Cell B, in the same row, also has candidates {4, 7}. That's a naked pair.
You don't know which cell gets the 4 and which gets the 7. But you know with absolute certainty that those two numbers belong to those two cells. No other cell in that row can contain 4 or 7.
The elimination: Remove 4 and 7 from every other cell in that shared row (or column, or box).
That's it. Simple concept, massive impact.
Why Are They Called "Naked"?
Because the pair is out in the open — "naked" for all to see. Both candidates are visible right there in the cells, with nothing else hiding alongside them.
This is in contrast to hidden pairs, where the two linked numbers are buried among other candidates in the same cells. Hidden pairs exist, but they're harder to spot (more on that later).
A Concrete Example
Imagine Row 3 of your puzzle. After filling in pencil marks, here's what the empty cells look like:
| Cell | Candidates | |------|-----------| | R3C1 | 2, 5, 8 | | R3C3 | 3, 5 | | R3C5 | 3, 5 | | R3C7 | 2, 8, 9 | | R3C9 | 2, 5, 9 |
See it? R3C3 and R3C5 both contain exactly {3, 5}. That's a naked pair.
Eliminations:
- Remove 5 from R3C1 → becomes {2, 8}
- Remove 5 from R3C9 → becomes {2, 9}
- 3 doesn't appear in other cells, so no additional eliminations for 3
Now R3C1 only has two candidates instead of three. That might not seem like much, but these small reductions cascade. Maybe {2, 8} in R3C1 creates a naked pair with another cell. Maybe reducing R3C9 to {2, 9} makes it a hidden single somewhere.
How to Spot Naked Pairs Fast
The Quick Scan Method
Look for cells with exactly two candidates. These are your potential pair members. Cells with three or more candidates can't be part of a naked pair.
Check for matches. When you find a two-candidate cell, scan the rest of its row, column, and box for another cell with the same two candidates.
Eliminate. When you find a match, remove both candidates from all other cells in that shared unit.
Frequency
Naked pairs appear in almost every medium, hard, and evil puzzle. In many cases, they appear multiple times. They're not rare — you just need to know what to look for.
On SudokuLovers.com, your pencil marks make naked pairs visually obvious. Two cells with the same small numbers? That's your signal.
Naked Triples and Beyond
The naked pair concept extends naturally:
Naked Triple: Three cells in the same unit containing a total of three candidates (distributed among them). Each cell has two or three of those candidates.
Example: Three cells contain {2, 5}, {2, 8}, and {5, 8}. Together, they claim 2, 5, and 8 for those three cells. Eliminate all three numbers from other cells in the unit.
Naked Quadruple: Same concept, four cells, four candidates. These are rare and harder to spot, but they exist.
The logic is always the same: N cells with the same N candidates means those candidates are locked to those cells.
Naked Pairs vs Hidden Pairs
Naked pair: Both cells show only the paired candidates. Easy to see.
Hidden pair: Both cells contain the paired candidates plus other stuff. Hard to see.
Example of a hidden pair:
- Cell A: {2, 5, 7, 9}
- Cell B: {2, 5, 6, 8}
If 2 and 5 don't appear as candidates in any other cell in that row/column/box, then A and B form a hidden pair on {2, 5}. You can remove all other candidates from both cells:
- Cell A becomes: {2, 5}
- Cell B becomes: {2, 5}
Which… turns it into a naked pair. Hidden pairs are just naked pairs in disguise.
Common Mistakes
Only checking rows. Naked pairs work in rows, columns, AND boxes. A pair in a 3x3 box is just as valid and useful as one in a row. Always check all three units.
Incomplete pencil marks. If you've missed a candidate in one of the pair cells (it should have three candidates but you only wrote two), you might "see" a naked pair that doesn't actually exist. Keep your pencil marks accurate.
Stopping after one. Puzzles often contain multiple naked pairs. After finding and applying one, re-scan the grid — the eliminations might have created new pairs.
Practice Drill
Here's how to build your naked pair spotting speed:
- Open a medium difficulty puzzle
- Fill in complete pencil marks for the entire grid
- Before doing anything else, scan every row, column, and box for cells with exactly two candidates
- Look for matches
- Apply eliminations and see how the puzzle opens up
Do this for a week, and naked pair spotting will become second nature. You'll start seeing them without even trying — they'll just pop out of the grid.
Why Naked Pairs Matter
Naked pairs are the foundation of advanced sudoku. Once you're comfortable with them, every other advanced technique makes more sense:
- X-Wings are essentially naked pairs across multiple rows
- Swordfish extends the pattern further
- Hidden pairs use the same logic in reverse
Master naked pairs, and you've unlocked the door to serious sudoku solving. Head to our medium puzzles and start practicing — you'll notice the difference immediately.