Mastering Intermediate Sudoku: Naked Pairs and Pointing Groups

Quick answer: Intermediate Sudoku is about relationships between candidate numbers. The two most powerful techniques are the naked pair (two cells sharing only the same two candidates) and the pointing pair (a candidate confined to one row or column within a box). Both let you eliminate candidates elsewhere.

Once you have mastered the basic scanning techniques, you will eventually hit a wall on medium-difficulty puzzles. When simple counting no longer works, it’s time to start looking for relationships between candidate numbers.

Transitioning from a beginner to an intermediate Sudoku player requires using pencil marks (noting potential numbers in the corners of cells) to spot hidden patterns. Here are the two most powerful intermediate strategies to help you break through.

1. The Naked Pairs Strategy

A Naked Pair occurs when two cells in the same house (a row, column, or 3x3 block) contain only the exact same two candidate numbers.

Because those two numbers must occupy those two cells, you can safely eliminate them as possibilities from every other cell in that same row, column, or block.

• How to spot it: Look for two cells in a single row that both contain only the notes [2, 7].
• The Action: If you see this, you don’t know which cell is 2 and which is 7 yet, but you do know no other cell in that row can be a 2 or a 7. Erase 2 and 7 from all other pencil marks in that row.

2. Pointing Pairs (or Pointing Groups)

Pointing Pairs happen when a candidate number appears inside a 3x3 block, but only within a single row or column of that block.

Since the number must live in one of those few cells inside that block, it cannot possibly exist anywhere else along that entire row or column outside of that block.

• How to spot it: Look inside a 3x3 block. Notice that the number 5 only appears as a candidate in the top row of that specific block.
• The Action: Follow that row across the rest of the entire Sudoku grid and eliminate 5 from the candidate lists of all other blocks in that row.

Quick Practice Tip

When playing on our app, turn on Automatic Pencil Marks to easily visualize these patterns without getting bogged down by manual notation!