How to Play Sudoku for Beginners
Sudoku looks intimidating at first — a 9×9 grid filled with numbers, no obvious starting point. But the rules are surprisingly simple, and once they click, you'll be hooked. This guide walks you through everything you need to know to solve your first puzzle.
What Is Sudoku?
Sudoku is a logic puzzle played on a 9×9 grid. The grid is divided into nine 3×3 boxes. Some cells already contain numbers — these are called clues or givens. Your job is to fill in the empty cells so that every row, every column, and every 3×3 box contains each of the digits 1 through 9 exactly once.
That's it. No math, no addition, no multiplication. Just logic.
The Three Rules
Every valid sudoku solution follows three rules:
- Every row must contain the digits 1–9, with no repeats.
- Every column must contain the digits 1–9, with no repeats.
- Every 3×3 box must contain the digits 1–9, with no repeats.
A number can only appear once in each row, once in each column, and once in each box. These three constraints together determine the entire solution — there is always exactly one correct answer.
Reading the Grid
When you look at a sudoku puzzle, you'll notice the grid has two kinds of cells:
- Clue cells — printed in bold or a darker color. These are fixed and cannot be changed.
- Empty cells — these are the cells you fill in.
The 9×9 grid is divided into nine 3×3 boxes. It helps to think of the grid as having three layers: rows (horizontal), columns (vertical), and boxes (the 3×3 sections). Every cell belongs to exactly one row, one column, and one box — and all three constraints apply to it simultaneously.
Your First Move: Find the Easy Cells
The best way to start a beginner puzzle is to look for cells that can only contain one possible number. Here's how:
- Pick any empty cell.
- Look at the row it belongs to — which digits 1–9 are already there?
- Look at the column — which digits are already there?
- Look at the 3×3 box — which digits are already there?
- Combine all three lists. If only one digit is missing, that's your answer.
On easy puzzles, you'll find several cells like this right away. Fill them in, and the new numbers you add will unlock more cells. The puzzle builds on itself.
A Simple Example
Imagine an empty cell in row 3. Row 3 already contains: 1, 2, 4, 5, 6, 7, 8, 9. That means only 3 is missing — so the answer for that cell is 3. You don't even need to check the column or box in this case.
This technique is called Last Remaining Cell or Full House. It's the easiest pattern in sudoku, and easy puzzles are full of them.
What to Do When You're Stuck
If no cell has an obvious answer, try a different approach: instead of looking at empty cells, look at a specific digit.
Pick the number 5, for example. Look at each of the nine 3×3 boxes. In boxes that don't have a 5 yet, check which empty cells could possibly hold a 5. If only one cell in a box is compatible with a 5 (because the row and column for every other empty cell already contain a 5), then that cell must be 5.
This technique is called Scanning, and it's the second most useful beginner skill after Last Remaining Cell.
Common Beginner Mistakes
- Guessing. Easy and medium sudoku puzzles never require guessing. If you feel like you have to guess, step back and look more carefully — there's always a logical deduction available.
- Forgetting one of the three constraints. It's easy to check the row and column but forget to check the 3×3 box, or vice versa. Always check all three before placing a number.
- Rushing. Sudoku rewards patience. A slow, systematic scan beats frantic searching every time.
Ready to Try?
The best way to learn sudoku is to play. Start with an easy puzzle — the clues are generous, and the logic chains are short. Once you can consistently solve easy puzzles, move up to medium.
Play a free Easy Sudoku puzzle →
When you're ready to go deeper, read: Sudoku Rules Explained →