How Many Sudoku Pencil Marks Should You Write?

Some solvers write every candidate; others note only pairs and suspicious cells. Both can work when the marks are accurate and the notation has a purpose.

Choose a system that reduces memory load without turning the grid into visual static.

Start with direct scanning

Do not fill the board before looking for singles. A few minutes of naked and hidden-single scanning can solve many cells and leave fewer notes to maintain.

Note the smallest cells first

Cells with two or three candidates and digits that are scarce in a unit usually give the best return. They are easier to compare and more likely to form a pair or a useful interaction.

Use full notes at a boundary

When direct progress stops, full candidates in one crowded box or band can reveal hidden singles. You do not need to annotate every empty cell at once; build a complete local picture, then move on.

Erase as soon as a digit is placed

A stale mark is worse than a missing one because it suggests a relationship that no longer exists. Update the affected row, column and box immediately, whether you are using a pencil or an onscreen notes mode.

Let clarity decide

If notes make the grid harder to read, remove low-value marks and keep only candidates that participate in a pattern. Your notes are working when they help you explain the next move.