Pointing Pairs in Sudoku: How to Spot and Use This Key Elimination Technique

You have worked through every naked single and hidden single. The grid is still stuck. Before reaching for guess-and-check, pause and look more carefully at your 3×3 boxes. Pointing pairs are one pattern to check: they let a restriction inside a box eliminate candidates along a row or column.

What Are Pointing Pairs in Sudoku?

A pointing pair occurs when a candidate digit appears in only two cells within a 3×3 box, and both of those cells are in the same row or column. Because that digit must go into one of those two cells, it cannot appear anywhere else in that shared row or column outside the box.

The name makes sense when you picture it: those two cells "point" along the row or column, acting like arrows that force eliminations down the line.

Worked example: Say the digit 4 can only go in two cells within the top-right box, and both cells happen to be in row 2. Wherever else a 4 appears as a candidate in row 2 — but outside that box — you can safely erase it. The 4 is locked inside that box's row-2 cells. This single move can trigger a cascade of new singles.

How to Spot a Pointing Pair (Step by Step)

1. Choose a digit. Pick any number still missing from several boxes.
2. Scan one box at a time. Inside the box, mark which cells still have that digit as a candidate.
3. Check alignment. If all those candidate cells share the same row, or all share the same column, you have a pointing pair (or pointing triple).
4. Eliminate. Remove that digit from every other cell in that row or column outside the box.
5. Repeat for other digits and boxes. After an elimination, update the notes and check whether another move is available.

Pointing Pairs vs Pointing Triples

The logic is identical whether two or three cells are involved. If a candidate appears in exactly three cells within a box and all three share the same row or column, that is a pointing triple. The elimination scope is the same: remove the candidate from the rest of that row or column outside the box.

Count every position for the chosen digit inside the box. Two aligned positions form a pointing pair; three form a pointing triple. A position elsewhere in the box breaks that alignment.

Pointing Pairs vs Box Line Reduction — Same Thing?

Almost. They are two directions of the same underlying logic, which is why some solvers call both "locked candidates."

• Pointing pairs work outward from the box: candidates confined to one row or column inside a box eliminate from the rest of that row or column.
• Box line reduction works inward from the line: candidates confined to one box inside a row or column eliminate from that box outside the original row or column.

Check both directions: start with a box for pointing, or with a row or column for claiming. The starting unit determines where elimination is allowed.

What Difficulty Level Uses Pointing Pairs?

Difficulty labels vary between puzzle publishers. Use a pointing pair whenever its candidate restriction holds, regardless of the label. It is not a prerequisite for hidden pairs; these are different patterns.

Try today’s Sudoku and choose a difficulty in the player. Practise explaining the box restriction before removing any candidate.

Common Mistakes

• Eliminating inside the box. Pointing pairs eliminate from outside the box along the shared row or column — not from the other cells inside the box itself.
• Partial alignment. If the candidate cells are not all in the same row or column, no pointing pair exists. Two cells diagonal to each other do not qualify.
• Skipping follow-up. After each elimination, re-scan for naked singles before moving on. An elimination may reveal a forced digit, but it need not produce an immediate placement.

Frequently Asked Questions

What are pointing pairs in Sudoku?

A pointing pair occurs when a candidate digit appears in only two cells within a 3×3 box, and both cells are in the same row or column. Because the digit must go in one of those two cells, it can be eliminated from all other cells in that row or column outside the box.

What is the difference between pointing pairs and box line reduction?

They are two directions of the same logic. Pointing pairs work from the box outward — candidates confined to one row or column inside a box eliminate from the rest of that row or column. Box line reduction works from the row or column inward — candidates confined to one box inside a row or column eliminate from that box outside the original row or column.

What is a pointing triple?

A pointing triple follows the same logic as a pointing pair but with three cells. If a candidate appears in exactly three cells within a box and all three share the same row or column, the digit can be eliminated from the rest of that row or column outside the box.

When should I use pointing pairs?

A practical routine is to check singles first, then look for box-line restrictions when progress stalls. You can use a pointing pair whenever the pattern is valid; there is no mandatory order between it and other elimination techniques.