Sudoku FlowHow Sudoku difficulty is rated
Updated 2026-10-05
Clues are not the measure
A puzzle with few givens can be easy if every step is a simple single, and a puzzle with more givens can be hard if it needs one difficult pattern. That is why some rating systems look at the techniques a solver uses rather than the number of clues.
Sources: HoDoKu: How puzzles are rated, What each Sudoku difficulty level asks of you
Rating by the hardest technique
One technique-based approach solves the puzzle the way a person would, always taking the easiest technique that makes progress, and records the hardest technique it had to use. Other systems also add up a score for every step. Either way the result depends on the solver: which techniques it knows and in which order it tries them.
Sources: HoDoKu: How puzzles are rated, What each Sudoku difficulty level asks of you
What 60,000 puzzles show
In the 60,000 puzzles in our app, the hardest technique our solver used was a hidden single for every Medium puzzle, a pointing pair for most Hard puzzles, and a pattern called ALS-XZ for most Extreme puzzles. Other apps and newspapers grade differently, so the same label can mean different things in different places.
Sources: What each Sudoku difficulty level asks of you
