How to Play Sudoku - Step by Step

Never played before? This guide walks you through everything - from reading the grid to placing your first numbers with confidence. No math required. Just logic.

Step-by-step visual walkthrough

  1. Step 1: Understand the grid

    You're looking at a 9×9 grid of cells, grouped into nine 3×3 boxes. Some cells are pre-filled - these are your givens (clues). They're fixed. Everything else is yours to solve.

    5 3 6 9 8 7

    Blue = row  ·  Green = column  ·  Amber = 3×3 box

  2. Step 2: Learn the three constraints

    The entire game is built on three rules:

    1. Each row contains 1–9, no repeats.
    2. Each column contains 1–9, no repeats.
    3. Each 3×3 box contains 1–9, no repeats.

    Every move you make must satisfy all three simultaneously.

  3. Step 3: Scan for easy cells first

    Look for rows, columns, or boxes that already have many givens. The fewer empty cells, the fewer candidates - making the right number easier to find.

    3 7 1 5 4 8 6 9

    One empty cell in this row - must be 2.

  4. Step 4: Use pencil marks (candidates)

    When a cell has more than one possible value, jot down small candidate numbers in the corners. This is how every serious solver works, at every difficulty level.

    1 4 7 9 eliminate 7

  5. Step 5: Eliminate and place

    Cross off candidates that appear elsewhere in the same row, column, or box. When only one candidate remains in a cell - place it. When a number can only fit in one cell within a group - that's where it goes (a hidden single).

    2 5 9 4 7 1 6 3 8

    7 can only go in the highlighted cell - every other cell is eliminated by the surrounding row or column.

  6. Step 6: Build momentum

    Each number you place opens new eliminations elsewhere. The puzzle accelerates as you go - if you get stuck, switch to a different region and come back.

  7. Step 7: Verify your solution

    When the grid is full, confirm: every row, every column, every 3×3 box contains 1–9 with no repeats. Congratulations. 🎉

What to learn next

Stuck mid-puzzle? See our step-by-step rescue guide or visit the Sudoku FAQ for quick answers.

How to play Sudoku - FAQ

What are the basic rules of Sudoku?

Each row, column, and 3×3 box must contain the numbers 1 to 9 without repeats. That's the entire game.

Is Sudoku a math puzzle?

No. It uses numbers as symbols, but there's no arithmetic. Pure logic is all you need.

How do you solve Sudoku step by step?

Start by scanning for cells with the fewest candidates, use pencil marks, eliminate options via row-column-box rules, and place numbers when only one candidate remains.

Can you guess in Sudoku?

A well-constructed Sudoku never requires guessing. If you feel the urge, you've probably missed an elimination somewhere.

What is a pencil mark?

A small candidate number noted in a cell to track which values are still possible. As you eliminate options, pencil marks narrow until the answer is clear.

How long does it take to solve a puzzle?

Beginners might spend 20–30 minutes on easy grids. Experienced solvers finish easy puzzles in 3–5 minutes. Hard puzzles can take 30 minutes or more.

What is the difference between easy and hard Sudoku?

Easier puzzles have more givens and can be solved with basic techniques. Harder puzzles have fewer givens and need advanced strategies like X-Wing or Swordfish.

What is a naked single?

A cell where only one number is possible after checking its row, column, and box. It's the first technique every beginner should learn. Read more →

What is a hidden single?

When a number can only fit in one cell within a row, column, or box - even if that cell still has other candidates. Read more →

Can Sudoku have more than one solution?

A proper Sudoku has exactly one unique solution. All puzzles in Sudoku a Day are verified to be unique.