How to Play Sudoku

Sudoku is a logic puzzle played on a 9×9 grid divided into nine 3×3 boxes. The goal is straightforward: fill every empty cell with a number from 1 to 9, so that each row, each column, and each 3×3 box contains every number from 1 to 9 exactly once. No number can repeat within the same row, column, or box. No mathematics is involved — only logic and deduction. Every sudoku puzzle begins with some numbers already placed in the grid. These pre-filled numbers are called givens or clues. The more givens a puzzle has, the easier it is to solve. An easy puzzle might start with 35 to 40 numbers already placed. An expert puzzle may have as few as 17 or 18, leaving the majority of the grid for you to work out. The three rules of sudoku are simple. First: each row must contain the numbers 1 through 9, each appearing exactly once. Second: each column must contain the numbers 1 through 9, each appearing exactly once. Third: each of the nine 3×3 boxes must contain the numbers 1 through 9, each appearing exactly once. Every deduction you make follows from these three constraints.

To get started, look for the easiest placements first. Find a row, column, or box that is nearly complete — if eight of the nine cells are already filled, the missing number is obvious. Work through all of these easy wins before attempting anything more complex. This approach gets more numbers on the board quickly and creates new deductions to work with. As you fill in more cells, you will start to see which numbers can possibly go in each remaining empty cell. When a cell has only one possible number given what is already in its row, column, and box, fill it in. This is the most fundamental sudoku technique and handles most easy puzzles on its own. Once you move beyond easy difficulty, you will need to think more carefully. Writing small candidate numbers in each empty cell — known as pencil marks or notes — helps you track possibilities and spot patterns that are impossible to see otherwise. From there, techniques like hidden singles, pointing pairs, and naked pairs let you eliminate candidates and make progress even when no single cell has an obvious answer. The guides in this section cover everything from the absolute basics to the rules, history, and benefits of sudoku. If you are completely new, start with the rules guide. If you have played before but want to get better, explore the strategy guides linked here and on our strategies page.