SudokuIQ Academy
How to Solve Sudoku: Rules and Techniques for Every Level
Sudoku looks simple: a 9x9 grid, the numbers 1 to 9, and no calculator required. The hard part is knowing what to do next when the easy answers stop appearing. This guide moves from beginner rules to practical solving techniques you can use immediately.
What Is Sudoku?
Sudoku is a logic-based number placement puzzle played on a 9x9 grid divided into nine 3x3 boxes. Some cells begin with numbers already filled in. These are called givens or clues. Your goal is to fill every empty cell so each row, column, and box contains the numbers 1 to 9 exactly once.
Despite the digits, Sudoku is not really a maths puzzle. The numbers act like symbols. You could replace 1 to 9 with letters or icons and the logic would stay the same.
The Rules of Sudoku
The single-solution rule is important. If you feel forced to guess, it usually means there is a hidden logic step you have not spotted yet.
Reading the Grid: Rows, Columns, and Boxes
Every cell belongs to exactly three units at the same time: one row, one column, and one 3x3 box. Solving Sudoku is mostly the art of using those three overlapping constraints to eliminate impossible candidates.
A candidate is a small possible number for a cell. Good note-taking makes harder strategies much easier to see.
Beginner Technique 1: Naked Singles
A Naked Single is a cell with only one legal candidate left after checking the row, column, and box. If a cell cannot be 1, 2, 3, 4, 6, 7, 8, or 9, it must be 5.
This is the safest first technique because the proof is local and direct. SudokuIQ Coach uses this kind of move as one of the first explanations for new players.
Beginner Technique 3: Scanning
Scanning means moving through the grid with a plan instead of jumping randomly. Pick a number, such as 5, then check each box to see where that number can still fit after row and column restrictions.
- Pick one number.
- Check each 3x3 box that does not contain it.
- Use existing rows and columns to rule out cells.
- If only one cell remains, place the number.
- Repeat with the next number.
Intermediate Technique: Naked Pairs and Pointing Pairs
A Naked Pair appears when two cells in the same row, column, or box contain the same two candidates and nothing else. Those two numbers must occupy those two cells, so you can remove them from the rest of that unit.
Pointing Pairs connect box logic with row or column logic. If a number can only appear in one row inside a box, that number can be removed from the rest of that row outside the box.
Common Mistakes Beginners Make
- Guessing instead of eliminating candidates.
- Scanning only rows and forgetting columns and boxes.
- Not using pencil notes when puzzles become harder.
- Forgetting to re-scan after every new placement.
- Rushing through 3x3 box logic.
Frequently Asked Questions
Do I need maths to solve Sudoku?
No. Sudoku uses digits as labels. It is a logic and pattern puzzle.
Is guessing ever necessary?
Not in a well-formed Sudoku. If you feel forced to guess, look for a missed elimination.
How do I get faster?
Practice systematic scanning, use candidates, and learn techniques in order.