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How to Play Sudoku

Sudoku looks tricky, but the rules fit in one sentence and there's no maths involved. Here's everything you need to start solving — and to enjoy it.

The one rule of Sudoku

A classic Sudoku is a 9×9 grid split into nine 3×3 boxes. Some cells are already filled in. Your job is to fill every empty cell so that:

• each row contains the digits 1–9 exactly once,
• each column contains the digits 1–9 exactly once, and
• each 3×3 box contains the digits 1–9 exactly once.

That's the whole game. No digit may repeat inside any row, column or box. Smaller grids work the same way — a 4×4 grid uses the digits 1–4, and a 6×6 grid uses 1–6.

A step-by-step guide for beginners

1. Pick an easy board. Start on an Easy 9×9 puzzle, or try a 4×4 grid to learn the idea fast.
2. Hunt for "only one option" cells. Look along a row, a column and a box at the same time. If eight of the nine digits already appear among them, the ninth must go in the empty cell.
3. Scan one digit at a time. Pick a number — say 5 — and see which boxes still need it. Often only one cell in a box can legally take it.
4. Use pencil notes. When a cell has a few possible digits, jot them down as notes. As you place numbers elsewhere, cross candidates off until one remains.
5. Never guess. A good Sudoku has exactly one solution you can reach by logic. If you're stuck, you've simply not spotted the next deduction yet — slow down and re-scan.

First solving techniques

Naked single

A cell where only one candidate remains after you've ruled out everything in its row, column and box. Fill it in — these are the bread and butter of every solve.

Hidden single

A digit that can legally go in only one cell of a row, column or box, even if that cell looks like it has other options. Scanning digit by digit reveals these quickly.

Want more? Our Sudoku tips & strategies guide walks through pointing pairs, naked pairs and the X-Wing.

Frequently asked questions