Sudoku Rules - How the Game Works
Sudoku has a reputation for looking mathematical, but the standard game uses logic, not arithmetic. You never add, subtract, or calculate totals. You only place digits where they can legally go according to three simple rules.
The Three Core Rules
- Each row must contain digits 1 to 9 exactly once.
- Each column must contain digits 1 to 9 exactly once.
- Each 3x3 box must contain digits 1 to 9 exactly once.
That means every time you place a digit, you must test it against all three units at the same time.
What Given Numbers Are
Given numbers are the digits already printed in the puzzle when the game begins. You do not change them. They are the fixed clues that make the puzzle solvable through logic.
What Makes a Valid Sudoku?
A valid standard sudoku has one unique solution. This matters because the puzzle should reward deduction, not random branching. It is also why clue count alone does not define difficulty: a puzzle may have many givens but still be tricky if the structure is awkward.
Common Rule Misconceptions
- Diagonal sudoku is a variant. Standard sudoku does not require digits 1 to 9 on the diagonals.
- The order of placements does not matter, only correctness does.
- Sudoku is not about sums. The digits behave as symbols with uniqueness constraints.
Frequently Asked Questions
What are the rules of sudoku?
Each row, column, and 3x3 box must contain digits 1 to 9 exactly once.
How many numbers are given in a sudoku puzzle?
That varies by puzzle. Easier boards usually have more givens than harder ones.
Can sudoku have two solutions?
A proper standard sudoku should have exactly one unique solution.
What is the minimum number of clues in sudoku?
The proven minimum is 17 clues for a valid standard puzzle with a unique solution.