Pointing and Claiming: the differences explained clearly

Pointing and Claiming are two very similar Sudoku techniques, which is exactly why they are often confused.

Both work with the relationship between boxes, rows and columns. Both allow you to eliminate candidates. Both are based on the idea that, if the possible positions of a number are concentrated at the intersection between a box and a line, that number can be eliminated from other connected cells.

The main difference is the starting point. Pointing starts from the box and produces eliminations on the row or column outside the box. Claiming starts from the row or column and produces eliminations inside the box.

In this guide, we will see the difference clearly, with examples and a simple pattern to remember.

Pointing and Claiming look similar because both involve a box and a line.

In both cases, you are observing a candidate number and trying to understand whether its possible positions are concentrated in one specific area of the grid.

The confusion comes from the fact that the final result is always a candidate elimination. However, the reasoning that leads to that elimination is different.

Understanding where the reasoning starts is the best way to distinguish the two techniques.

In Pointing, you always start from a box.

You look at a 3×3 box and choose a candidate number. If all possible positions of that number in the box are on the same row or the same column, then the number of the box must be on that line.

At that point, you can eliminate that candidate outside the box, along the same row or column.

The line receives the information. The eliminations happen outside the box.

In Claiming, instead, you start from a row or a column.

You look at a line and choose a candidate number. If all possible positions of that number in the line are concentrated inside the same box, then that number of the line must be in that box.

At that point, you can eliminate that candidate from the other cells of the box.

The line gives you the information. The box receives the elimination.

This is the most important difference compared with Pointing.

In Pointing, you eliminate outside the box.

If inside the box the candidates for a number are all on the same row, you eliminate that number from the other cells of the row outside the box. If they are all on the same column, you eliminate it from the other cells of the column outside the box.

In Claiming, you eliminate inside the box.

If in a row or column a number can go only inside one box, you eliminate that number from the other cells of the box that do not belong to the line.

This difference in eliminations is essential. Applying the elimination in the wrong direction can lead you to remove valid candidates.

If you confuse Pointing and Claiming, ask yourself where the reasoning started.

• If you started by looking at a box and noticed candidates aligned on a row or column, it is Pointing.
• If you started by looking at a row or column and noticed candidates concentrated inside a box, it is Claiming.

The direction of the reasoning also tells you where to eliminate: Pointing eliminates outside the box, Claiming eliminates inside the box.

Imagine a box where number 3 can go only in two cells. Both are on the same row.

Since the box must contain a 3, and the only possible positions are on that row, the 3 of the box will certainly be on that row.

Therefore, on the same row, outside that box, 3 cannot appear. You can eliminate candidate 3 from the other cells of the row outside the box.

This is Pointing because the reasoning starts from the box.

Now imagine a row where number 8 can go only in two cells. Both of these cells are in the same box.

Since the row must contain an 8, and 8 can go only in that box, then the 8 of the row will certainly be inside that box.

As a result, in the box, the other cells that do not belong to the row cannot contain 8. You can eliminate candidate 8 from those cells.

This is Claiming because the reasoning starts from the row.

This table summarizes the main difference. If you are confused, always ask yourself: am I starting from a box or from a line?

Pointing and Claiming are intermediate techniques based on the interaction between boxes, rows and columns.

Pointing starts from the box and lets you eliminate candidates outside the box along a row or column. Claiming starts from a row or column and lets you eliminate candidates inside a box.

Understanding this direction of reasoning is the simplest way to apply them correctly and use them in medium Sudoku without confusion.