Getting Started on Sudoku

If you are new to Sudoku, welcome to one of the most popular puzzles in the world!

Once you do a few Sudoku puzzles, you will quickly see why they are so appealing. But to get you started, here are a few of the best reasons:

• Sudoku puzzles are solved entirely with logic. There is no luck or guessing ever needed to solve one.
  
  
• Every player is equal. You need no math skills, no vocabulary skills, no scientific training. When it comes to solving one, every person is equal to the next.
  
  
• Sudokus come at every skill level, so you never feel over- or under-challenged.
  
  
• Each puzzle is unique, and as millions would tell you, you never get tired of doing them.

Most commonly, a Sudoku is a 9x9 grid, made up of nine 3x3 subgrids, or "regions." That means that a Sudoku grid has 81 cells total and that each region, row, and column has 9 cells.

In a Sudoku puzzle, some cells of the grid come with the numbers 1 to 9 already inserted. Your task is to place a number in each of the remaining cells of the grid following just one rule: Each column, row, and region must contain the numbers 1 to 9 exactly once.

For example, if a cell has the number 5 in it, then there cannot be another 5 in the row, column, and region that it sits in. It's really that simple.

There are many methods to determine what number goes in a cell, but the first two to focus on are these:

Counting: Take a blank cell. Look at every number in its row, column, and region. Often, you will find that many of the numbers 1 to 9 are already there. In some cases, you will find that 8 of the 9 numbers are there; in those cases, you know that the cell must get the 9th number. For example, say you have a blank cell and elsewhere in its row are 1, 4, and 7; in its column are 2, 8, and 9; and elsewhere in its region are 3 and 5. By elimination, you know that the cell must get the number 6.

Nearby Values: In this method, you focus on a single number at a time. The process entails scanning the rows of three adjacent regions to see whether a certain number appears in two of them. If yes, you immediately know in which region and row the number must appear again. The second step then would be to review the columns that lead into the cells in which the number must go. Often, you'll discover that the number is already in some of the columns, allowing you to determine in which cell that number must go.

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