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

Pointing pairs are one of the first intermediate Sudoku techniques worth learning. Once you have exhausted naked and hidden singles, a pointing pair is often the move that breaks a stalled grid. This guide explains what pointing pairs are, how to find them quickly, and how they relate to box-line reduction — a technique often confused with them.

What Are Pointing Pairs in Sudoku?

A pointing pair occurs when a candidate number appears in only two cells within a 3×3 box, and those two cells share the same row or column. Because the number must go in one of those two cells, it is effectively "locked" to that row or column inside the box. That lock lets you eliminate the same candidate from every other cell in the same row or column outside the box.

In formal Sudoku terminology this is called Locked Candidates Type 1. The name "pointing pair" comes from the idea that the two candidate cells point outward — along a row or column — to signal where eliminations can be made.

For a deeper look at the full rule set, see the Pointing Pairs strategy page.

How to Spot a Pointing Pair (Step-by-Step)

The scan is systematic. Work through each box one at a time:

1. Pick one 3×3 box. Focus only on that box for now.
2. Choose a candidate digit (1–9). Check which cells in the box still contain that digit as a candidate.
3. Count and check alignment. If the digit appears in exactly 2 (or 3) cells and those cells all sit in the same row, or all sit in the same column, you have found a pointing pair (or pointing triple).
4. Eliminate along the pointing line. Remove that candidate from every other cell in that row or column — but only outside the current box. Never touch the cells inside the box.
5. Move to the next digit, then the next box. Repeat until you have covered all nine boxes and all nine digits.

Check candidate positions carefully; there is no required speed. A systematic pass through digits and boxes can help you notice a pattern you previously missed.

Pointing Pairs vs Pointing Triples

The logic is identical whether two or three cells are involved:

• A pointing pair has exactly 2 aligned candidate cells in the box.
• A pointing triple has exactly 3 aligned candidate cells in the box.

Both use the same rule: the box must place the digit somewhere on that line. Other candidate positions in the box may have been ruled out by given digits or earlier deductions; a pointing triple does not require placed digits in the other rows.

A row or column intersects a 3×3 box in only three cells. Four candidate positions in that box cannot all lie on one line, so they do not form a pointing pair or triple.

Pointing Pairs vs Box-Line Reduction — Same Thing?

These two techniques are often confused because they are mirror images of each other. Both fall under the "Locked Candidates" family, but they start from opposite directions:

• Pointing Pairs (Type 1): start with the box. When a candidate inside a box is confined to one row or column, eliminate it from that row or column outside the box.
• Box-Line Reduction (Type 2): start with the row or column. When a candidate in a row or column only appears in cells belonging to one box, eliminate it from the rest of that box.

A useful mental shortcut: pointing pairs point outward from the box, while box-line reduction draws inward to the box. Neither is harder than the other — they are complementary. Always scan for both when you work through a grid.

Practice Example (Beginner-Friendly)

Consider Box 4 (the middle-left 3×3 box, covering rows 4–6 and columns 1–3). Suppose your pencil marks show that the digit 4 appears as a candidate only in two cells: row 4 col 2, and row 4 col 3.

Both cells are in row 4. That means 4 is a pointing pair locked to row 4 within Box 4.

Elimination: Remove 4 as a candidate from every cell in row 4 that lies outside Box 4 — that is, columns 4 through 9 of row 4. If any of those cells had 4 as a candidate, cross it out.

After that elimination, check whether any cell in row 4 now has only one candidate left. If so, you have just revealed a naked single — place that digit immediately and continue solving.

What Difficulty Level Uses Pointing Pairs?

Difficulty labels such as Medium vary between publishers. Look at the candidate pattern itself: pointing can help whenever all remaining positions for a digit in a box share one line, whatever the puzzle label.

If pointing gives no elimination, inspect other patterns such as naked pairs and hidden pairs. A pattern is useful only when it removes an actual candidate or justifies a placement; its name alone does not guarantee progress.

Ready to practice? Try today's daily Sudoku and actively look for pointing pairs as you solve.

Frequently Asked Questions

What are pointing pairs in sudoku?

A pointing pair has exactly two remaining positions for one digit in a box, both on the same row or column. Three aligned positions form a pointing triple. Either pattern rules out the digit elsewhere on that line outside the box.

How do I spot a pointing pair?

For each box, look at a single candidate digit and check which cells it appears in. If all its appearances in that box align in one row or one column, you have a pointing pair or triple. Now eliminate that candidate from the rest of that row or column.

What is the difference between pointing pairs and locked candidates?

They are two names for the same logical pattern. Locked candidates is the general term; pointing pairs specifically describes the case where candidates in a box point to a row or column. Box-line reduction is the reverse: candidates in a row or column are confined to one box.