How to Use Notes in Sudoku: A Simple Pencil Mark Guide for Beginners

How to use notes in Sudoku comes down to one simple habit: write the possible digits for an empty cell, then remove those possibilities as the grid gives you new information. Notes, also called pencil marks, help you stop guessing, see forced moves faster, and prepare for strategies that depend on clean candidates.

If you want the short answer, use notes only after you have scanned for obvious moves, keep them accurate, and clean them up every time you place a number. Good notes make Sudoku easier. Messy notes make it harder.

Quick Answer: How Do You Use Notes in Sudoku?

To use notes in Sudoku, look at an empty cell and write only the digits from 1 to 9 that do not already appear in the same row, column, or 3×3 box. Those digits are the cell’s candidates. As soon as you place a number elsewhere in the grid, remove that digit from all affected notes in the matching row, column, and box.

Featured snippet answer: use notes in Sudoku by marking every legal candidate in an unsolved cell, then updating those candidates after each confirmed placement.

What Are Notes in Sudoku?

Notes in Sudoku are small candidate numbers written inside unsolved cells. Some apps call them notes. Printed puzzle books often call them pencil marks. Both mean the same thing.

Example: if a blank cell cannot be 1, 2, 4, 6, 8, or 9 because those digits already appear in its row, column, or box, the remaining legal digits might be 3, 5, and 7. Those are the notes for that cell.

If you are new to candidate language, read What Is a Candidate in Sudoku? first. Notes are simply the written form of those candidates.

When Should You Start Using Notes?

Beginners usually make one of two mistakes: they avoid notes for too long, or they fill the entire grid with notes immediately. Both extremes slow you down.

A better routine is:

1. Scan for easy placements first.
2. Add notes when the next move is no longer obvious.
3. Expand notes gradually if the puzzle still does not open up.

On easy puzzles, you may need only a few notes. On medium and hard puzzles, fuller candidate lists become much more useful.

How to Use Notes in Sudoku Step by Step

1. Pick one unsolved cell

Choose an empty cell in a row, column, or box that already has a lot of digits filled in. Constrained cells are easier to analyze than wide-open ones.

2. Check the row

Cross off any digits already present in the row. Those digits cannot go in the cell.

3. Check the column

Now remove any digits already present in the column.

4. Check the 3×3 box

Remove any remaining digits that already appear in the cell’s box.

5. Write the remaining candidates

The digits left over are the valid notes for that cell. If only one digit remains, the cell is already solved and you should place it instead of keeping notes.

6. Update notes after every placement

This is the step many players skip. If you place a 7 in row 5, every other note containing 7 in row 5, its column, and its box must be cleaned up. Outdated notes create false patterns and fake difficulty.

A Simple Example of Sudoku Notes

Imagine cell r4c6 is empty.

• Its row already contains 1, 3, 5, and 8.
• Its column already contains 2, 5, 6, and 9.
• Its 3×3 box already contains 1, 4, and 8.

Start with digits 1 through 9. Remove the digits blocked by the row, column, and box. The remaining valid candidates are 7 and 9. Your note for that cell becomes {7,9}.

If you later place a 9 elsewhere in the same row, then r4c6 can only be 7. Your notes helped expose a forced move without guessing.

Should You Fill Notes in Every Empty Cell?

Not always. Full notation can be useful on harder puzzles, but it also creates clutter if you do it too early.

For most beginners, this progression works better:

• Start with partial notes in the most constrained cells.
• Look for singles and easy eliminations.
• Add broader notes only when progress slows down.

If you want a deeper comparison, see Snyder Notation vs Full Notation in Sudoku. The best note system is the one that keeps the board readable while still showing enough information.

How Notes Help You Solve Harder Sudoku

Notes do more than store possibilities. They reveal structure. Once candidate lists are visible, you can spot:

• naked singles, where one cell has only one candidate left,
• hidden singles, where one digit appears in only one place inside a row, column, or box,
• pairs, where two cells share the same restricted candidates, and
• locked candidates, where a digit is confined to one line inside a box.

That is why clean note-taking is not a side trick. It is the foundation of logical solving beyond the easiest puzzles. If you want the broader sequence, pair this guide with Sudoku Strategies for Beginners.

The 5 Most Common Notes Mistakes

1. Writing notes before checking for easy singles

If a cell is already forced, writing notes is wasted effort. Always scan first.

2. Leaving old candidates behind

Stale notes are one of the fastest ways to get stuck. When the grid changes, your notes must change with it.

3. Filling every cell too early

Too many notes too soon create visual noise. Start where the puzzle is most constrained.

4. Treating notes like guesses

Notes are possibilities, not predictions. A cell with {2,5,8} is not “probably 5.” It is simply limited to those three options for now.

5. Forgetting to re-scan after an elimination

Once notes change, new moves often appear immediately. Re-check the affected row, column, and box before moving on.

If this sounds familiar, review Common Sudoku Mistakes for Beginners next.

Best Notes Routine for Beginners

1. Scan rows, columns, and boxes for obvious singles.
2. Add notes only where the next move is unclear.
3. After every placement, clean the affected row, column, and box.
4. Look again for singles before hunting larger patterns.
5. Only expand into fuller notation when the puzzle truly needs it.

This routine keeps the board readable and prevents the classic problem of having too many notes to see anything useful.

Are Notes Necessary in Every Sudoku?

No. Easy puzzles can often be solved with scanning alone. But as difficulty rises, notes become much more useful. Medium puzzles often benefit from partial notes. Hard puzzles usually require consistent candidate tracking.

A practical rule is simple: use the lightest amount of notation that still lets you solve logically.

FAQ: How to Use Notes in Sudoku

What are notes in Sudoku?

Notes are small candidate numbers written in unsolved cells to show which digits are still possible.

How do beginners use notes in Sudoku?

Beginners should first scan for obvious moves, then write candidates only in cells where the next move is unclear. Keep those candidates updated after every placement.

Should I use full notes or partial notes?

Use partial notes on easier puzzles and fuller notes when candidate relationships start to matter. The goal is clarity, not writing the most numbers.

Are notes the same as guessing?

No. Notes list legal possibilities based on Sudoku rules. Guessing means choosing one option without enough proof.

What techniques depend on notes?

Most intermediate and advanced techniques depend on notes, including pairs, triples, locked candidates, fish patterns, and chain-based logic.

Conclusion: Clean Notes Make Better Sudoku Solves

How to use notes in Sudoku is not really about writing more numbers. It is about organizing the right information at the right time. When notes are clean, updated, and used selectively, they help you solve with logic instead of guesswork.

If you want to build this habit quickly, open a fresh puzzle on Pure Sudoku and focus on one rule: every time the grid changes, your notes should change too. That single habit makes almost every later technique easier to learn.