Pointing Pairs
When a digit within a box can only appear in one row or column — eliminate it from that row or column outside the box.
What is Pointing Pairs?
A Pointing Pair (or Pointing Triple) is one of the most powerful intermediate Sudoku intersection techniques. It occurs when a candidate digit within a 3×3 box is restricted to exactly two (or three) cells that all lie in the same row or column. Because that digit must go in one of those cells (since it must appear somewhere in the box), it cannot appear in any other cell along that same row or column outside the box. This "pointing" relationship lets you eliminate the digit from cells in the row or column that are outside the box, even without knowing exactly which cell in the box will receive the digit. The technique bridges two important constraint types — box constraints and line constraints — and is especially valuable because its eliminations often affect cells in adjacent boxes, potentially revealing new patterns in those areas. Pointing Pairs and their triple variant are critical for solving Hard puzzles and are a prerequisite for understanding more advanced intersection techniques like X-Wing.
When to Use Pointing Pairs
Use Pointing Pairs after exhausting all Singles and once you have a fully annotated candidate grid. For each 3×3 box, cycle through each unplaced digit and identify where within the box that digit can still appear. If all remaining candidate cells for that digit in the box share the same row (or column), the technique applies. This is most fruitful when examining boxes that have several digits already placed — with fewer empty cells in the box, it is more likely that a digit's remaining candidates will align in a single row or column. After applying the technique, always re-scan the modified row or column for newly revealed singles or other patterns.
How to Apply Pointing Pairs — Step by Step
- 1
Examine a box and select a digit
Pick a 3×3 box that has several placed digits. For that box, choose a digit that has not yet been placed. You'll analyze where in the box this digit can go.
- 2
Find all candidate cells for that digit within the box
In the selected box, identify every empty cell that could contain the chosen digit. A cell is a valid candidate if the digit does not appear in that cell's row, column, or the box itself. Pencil marks make this step straightforward — simply look for which cells in the box have that digit as a candidate.
- 3
Check for row or column alignment
Look at the candidate cells you found. Are they all in the same row? Or all in the same column? If the answer is yes to either question, you have found a Pointing Pair (if two cells) or Pointing Triple (if three cells). If the candidates are spread across multiple rows and multiple columns, the technique does not apply for this digit in this box — move on to the next digit.
- 4
Eliminate from the line outside the box
Since the digit must land in one of the aligned candidate cells inside the box, it cannot appear in any other cell on that same row or column beyond the box. Remove this digit from the candidates of every other cell along the shared row (or column) that lies outside the box. This is the key elimination step.
💡 Pro Tip
Pointing Pairs are most effective in boxes where a digit has only two or three candidate cells remaining. Start by scanning boxes with lots of placed digits. A quick mental shortcut: if you can see that a digit appears in a box in two cells in the same row, immediately look along that row outside the box for cells that also show that digit as a candidate — those candidates are eliminated. Similarly, scan for the column-aligned version. Building this reflex — "check for pointing pairs whenever a box is nearly full" — dramatically speeds up your solving.
Practice Pointing Pairs Now
Put this technique to the test on a live puzzle. The Practice Mode lets you work through real examples with candidate marking.