Pointing Triples Sudoku Technique

James Hoss

Sudoku Expert & Puzzle Designer

Published March 13, 2025 Updated June 4, 2025 7 min read

The pointing triple is an intermediate Sudoku technique that extends the logic of pointing pairs to three cells. If you understand pointing pairs, you already know the core concept — pointing triples simply apply the same principle when a candidate is locked to three cells in a single row or column within a 3×3 box. The elimination power is identical.

Prerequisites

Before learning pointing triples, you should understand:

• Candidate notation (pencil marks) — all possible values listed in each empty cell
• Naked singles and hidden singles — basic solving fundamentals
• Pointing pairs — the two-cell version of this same technique

What is a Pointing Triple?

A pointing triple occurs when a candidate number inside a 3×3 box appears in exactly three cells, and all three cells are aligned in the same row or same column. Because the candidate is locked to that line within the box, it must be placed in one of those three cells. This means you can eliminate the candidate from every other cell in that row or column outside the box.

Pointing Triple vs. Pointing Pair

The elimination step is exactly the same — remove the candidate from the rest of the line outside the box. The only difference is the number of cells involved. In practice, pointing pairs are more common because it’s more likely for a candidate to be restricted to two cells than three.

How to Find Pointing Triples: Step-by-Step

Step 1: Examine a 3×3 Box

Pick any box and look at the pencil marks inside it. For each candidate digit present in the box, count how many cells contain it and note their positions.

Step 2: Check for Three-Cell Alignment

If a candidate appears in exactly three cells within the box, check: Are all three cells in the same row or the same column?

• If the three cells span different rows AND different columns — no pointing triple
• If all three cells share a single row or column — pointing triple found

Step 3: Eliminate from the Rest of the Line

Remove the candidate from every cell in that row (or column) that is outside the current box. The three cells inside the box keep their candidates.

Worked Example 1: Row-Based Pointing Triple

Consider the bottom-left 3×3 box (Box 7). After completing pencil marks:

Examining the candidate 6 in Box 7:

• 6 appears in Row 7, Col 1
• 6 appears in Row 7, Col 2
• 6 appears in Row 7, Col 3
• 6 does NOT appear in any Row 8 or Row 9 cells within this box

All three instances of 6 are in Row 7. Since one of these three cells must contain 6, we can eliminate 6 from all cells in Row 7 outside of Box 7 — that means removing 6 from any cells in Row 7, columns 4–9.

Worked Example 2: Column-Based Pointing Triple

Consider the top-right 3×3 box (Box 3):

Looking at candidate 3 in Box 3:

• 3 appears in Row 1, Col 8
• 3 appears in Row 2, Col 8
• 3 appears in Row 3, Col 8
• 3 does NOT appear in Col 7 or Col 9 within this box

All three instances are in Col 8. Eliminate 3 from every cell in Col 8 outside of Box 3 — specifically from rows 4–9 in column 8.

This elimination could immediately reveal a hidden single for 3 in another box, or reduce a cell to a naked single, cascading further progress.

The Logic Behind Pointing Triples

The logic is the same as pointing pairs, just applied to three cells:

1. Box constraint: 6 must appear exactly once in Box 7
2. Within Box 7, 6 can only go in Row 7 (columns 1, 2, or 3)
3. Therefore, 6 is guaranteed to be in Row 7 somewhere in columns 1–3
4. Row constraint: 6 can only appear once in Row 7
5. Conclusion: No cell in Row 7 outside columns 1–3 can contain 6

This is sometimes called “locked candidates Type 1” — the candidate is locked to a specific line within a box.

Pointing Triple vs. Box-Line Reduction

Just like pointing pairs, pointing triples have a mirror technique:

Both are “locked candidates” techniques. When you scan a box and find a pointing triple, also check the reverse — scan the line to see if all candidates in that line fall within one box (box-line reduction).

Common Mistakes to Avoid

1. Eliminating from inside the box. Only remove the candidate from cells outside the box, along the shared row or column. The three cells inside the box must keep the candidate.

2. Confusing with naked triples. A naked triple involves three cells sharing three candidates within a unit. A pointing triple involves one candidate locked to one line within a box. They’re completely different techniques.

3. Missing column-based patterns. Always check both row and column alignment. Solvers who only scan horizontally miss half the pointing triples.

4. Not having accurate pencil marks. Like all candidate techniques, pointing triples require complete and correct pencil marks. A wrong pencil mark can lead to incorrect eliminations.

5. Overlooking the cascade. After eliminating candidates from a pointing triple, immediately re-check the affected cells. New singles or pairs often appear right away.

Tips for Finding Pointing Triples Efficiently

• Check boxes after placing digits. When you fill in a cell, the candidate lists in neighboring boxes shrink, sometimes creating new pointing triples.
• Focus on boxes with few empty cells. A box with only 3–4 empty cells makes it trivial to check candidate alignment.
• Scan systematically. Work through all nine boxes in order, checking each candidate. This disciplined approach prevents you from missing subtle patterns.
• Combine with pointing pair scanning. Since you’re already checking for pointing pairs, also check if a third cell aligns — it costs no extra effort.

When to Use Pointing Triples

Pointing triples sit at the same level as pointing pairs in the solving hierarchy:

1. First: Naked singles and hidden singles
2. Then: Pointing pairs and pointing triples
3. Next: Naked pairs and hidden pairs
4. Later: X-Wings, Swordfish, and wings

Pointing triples appear less frequently than pointing pairs because having three cells align is less statistically likely than two. However, they appear regularly in Hard and Expert puzzles.

Frequently Asked Questions

How common are pointing triples compared to pointing pairs?

Pointing pairs are roughly 2–3× more common. Pointing triples require a candidate to appear in exactly three cells within a box, all aligned — which is a more restrictive condition. Still, they appear often enough in Medium, Hard, and Expert puzzles that you should always scan for them.

Is a pointing triple stronger than a pointing pair?

Not necessarily — both produce the same type of elimination (removing a candidate from cells along a line). The “strength” depends on how many candidates get eliminated and what that enables. Sometimes a pointing pair eliminates more candidates than a pointing triple, depending on the puzzle state.

Can I have a “pointing quadruple”?

No — a 3×3 box only has three cells per row and three cells per column. So the maximum aligned cells for a pointing pattern is three (a pointing triple). If four cells had the same candidate, they’d span at least two rows and two columns, which doesn’t form a pointing pattern.

Do pointing triples appear in easy puzzles?

Rarely. Easy puzzles are typically solvable with singles alone. You’ll start encountering pointing triples regularly in Medium and Hard puzzles.

Practice Pointing Triples

Ready to apply this technique? Try our Hard or Expert difficulty puzzles where pointing triples frequently appear.