How to Solve Sudoku: A Step-by-Step Guide for Beginners

If you've ever stared at a Sudoku grid wondering where to even begin, this is for you. Learning how to solve Sudoku takes about ten minutes, and there's no math involved. The numbers are just symbols. You could swap them for nine colors or nine animals and nothing would change. What you actually need is one rule and a couple of simple habits. Let's get you solving your first puzzle today.

The rules in 60 seconds

A Sudoku board is a 9x9 grid, split into nine 3x3 boxes. Some cells already hold numbers (those are your clues). Your job is to fill the rest so that:

• every row contains the digits 1 to 9, with no repeats,
• every column contains 1 to 9, no repeats,
• every 3x3 box contains 1 to 9, no repeats.

That's the entire game. One of each number in every row, column, and box. If you want the formal version with examples, the Sudoku rules page lays it all out.

How to read the grid

Before you place anything, get comfortable seeing the three units a cell belongs to. Every empty cell sits in one row, one column, and one box at the same time. Whatever you write there has to be legal in all three. That overlap is the whole source of the puzzle's logic, and your way in.

Your first move: scanning

The easiest way to start is scanning. Pick a number that already shows up a few times on the board, say 5. Now look at each 3x3 box that doesn't have a 5 yet. A 5 can't go in any row or column that already contains one, so mentally cross those lines out. If a box has only one cell left where a 5 could legally sit, that's your answer. Write it in.

Work through all nine boxes for that number, then move to the next number. This one technique, called cross-hatching, will solve most of an easy puzzle on its own.

Filling forced cells

After scanning, look for cells that have only one possible number left. Pick an empty cell and ask which digits are already in its row, its column, and its box. Cross all of those off the list of 1 to 9. If exactly one digit survives, it's forced, and it has to go there.

These two moves, scanning and checking forced cells, are enough to finish every easy puzzle we have. You don't need anything fancier yet.

A quick worked example

Say a 3x3 box is missing the numbers 2, 6, and 8, across three empty cells. You check the first empty cell: its row already has a 6, and its column already has an 8. That leaves only 2, so the 2 is forced into that cell.

Now the box only needs 6 and 8 in two cells. You look at the next empty cell: its column contains a 6, so 6 can't go there, which means it must be 8. And the last cell takes the 6 by elimination. Three cells solved, no guessing, just the rule doing the work. String enough of these together and the grid fills itself in.

What to do when you get stuck

Every beginner hits the same wall: you scan, you fill the obvious cells, and then nothing jumps out. Here's the fix.

• Re-scan slowly. You almost certainly skipped a number. Go 1 through 9 again, deliberately.
• Look for hidden singles. Sometimes a cell has a few candidates, but one of those digits has nowhere else to go in the row, column, or box. That cell is solved even though it didn't look obvious.
• Start writing pencil marks. Jot the possible numbers into each empty cell. Seeing the options on paper turns a memory problem into a spotting problem. There's a whole guide on pencil marks if you want to do it cleanly.

And the golden rule: never guess. Our puzzles always have exactly one solution reachable by logic. If something feels like a coin flip, there's a deduction you haven't found yet, so keep looking.

Common beginner mistakes

A few things trip up almost everyone early on:

• Forgetting the box. New solvers check the row and column but forget the 3x3 box counts too. All three, every time.
• Trusting a guess. One guessed cell can feel fine for ten moves, then collapse the whole grid. Back to square one.
• Sloppy pencil marks. If you're going to mark candidates, keep them accurate. A single stale candidate you forgot to erase will send you down the wrong path.

Where to go next

Once scanning and forced cells feel natural, you're ready to climb. Medium puzzles introduce hidden singles. Hard puzzles bring in pairs and triples. The full progression, with every technique in order, lives in the Sudoku strategy guide.

The best way to learn how to solve Sudoku is to solve Sudoku. Open an easy grid, scan for your first number, and go.

Frequently asked questions

Is there any math in Sudoku?

No. The digits are just symbols, and you never add or multiply anything. Swap them for nine colors and the puzzle works exactly the same. It's pure logic.

What is the first thing to do in a Sudoku puzzle?

Scan for the digit that already appears most often on the board. The more copies are placed, the more likely you'll find a box where only one cell can legally take it.

Can every Sudoku be solved without guessing?

A proper Sudoku has exactly one solution reachable by logic, so yes. If you feel the urge to guess, there's a deduction you haven't spotted yet. Re-scan instead.

How long should an easy Sudoku take?

Once scanning feels natural, a few minutes. If you can finish an easy grid in under five minutes without hints, you're ready for medium.