Master the art of Sudoku with our comprehensive guide. Learn the rules, strategies, and techniques to solve puzzles like a pro.
Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids (also called "boxes" or "blocks") contains all of the digits from 1 to 9.
The puzzle setter provides a partially completed grid, which typically has a unique solution. Completed puzzles are always a type of Latin square with an additional constraint on the contents of individual regions.
The Sudoku grid consists of 81 cells arranged in a 9×9 square, divided into nine 3×3 subgrids.
You can only use numbers from 1 to 9. Each number must appear exactly once in each row, column, and 3×3 box.
Each horizontal row must contain the digits 1-9 exactly once, with no repetitions.
Each vertical column must contain the digits 1-9 exactly once, with no repetitions.
Each 3×3 subgrid must contain the digits 1-9 exactly once, with no repetitions.
A valid Sudoku puzzle has only one solution that can be reached through logical deduction, not guessing.
This is the most basic Sudoku solving technique. When eight out of nine cells in a row, column, or 3×3 box are filled, the remaining cell must contain the missing number.
Tip: Start by scanning rows, columns, and boxes to find cells with only one possible number.
If a number can only go in one cell within a row, column, or box, that cell must contain that number. This technique helps eliminate possibilities.
Tip: Look for numbers that appear frequently in adjacent rows or columns to narrow down possibilities.
For a specific cell, check which numbers are already present in its row, column, and 3×3 box. The missing number is the only possibility for that cell.
Tip: This is perfect for beginners. Systematically check each empty cell's constraints.
When you're stuck, use notes to mark all possible numbers for each empty cell. This helps visualize possibilities and identify patterns. Fill in all potential candidates based on what's already in the row, column, and box.
Tip: Use notes systematically. Start with cells that have the fewest possibilities.
After placing notes, you may find cells where only one number is possible. This is called a "naked single" - the cell can only contain that one number.
Tip: Regularly scan your notes to find naked singles. They're easy wins!
When two cells in the same row, column, or box can only contain the same two numbers, those numbers can be eliminated from other cells in that unit. This helps narrow down possibilities.
Tip: Look for pairs of cells with identical note sets. This is a powerful elimination technique.
Begin with easier difficulty levels to understand the patterns and build confidence before tackling harder puzzles.
Sudoku is about logic, not speed. Take your time to analyze each move carefully and avoid mistakes.
Don't fill in notes for every cell. Focus on cells with fewer possibilities first to maintain clarity.
Develop an eye for common patterns. The more you practice, the faster you'll recognize solving opportunities.
Now that you understand the rules and techniques, put your skills to the test! Start with an easy puzzle and work your way up to expert level.