Sudoku Statistics & Facts

Behind every 9×9 grid is a fascinating mathematical universe. Sudoku has been studied by mathematicians, computer scientists, and cognitive researchers for decades. Here are the numbers that define the game.

How Many Sudoku Grids Exist?

The total number of completed, valid 9×9 Sudoku grids — ignoring rotations, reflections, and relabeling of digits — is 6,670,903,752,021,072,936,960. That's approximately 6.67 × 1021, or 6.67 sextillion. This number was calculated in 2005 by Bertram Felgenhauer and Frazer Jarvis through an exhaustive enumeration using symmetry reductions and computational verification.

If you count grids that are "essentially different" — factoring out symmetries like digit permutation, band/row swapping, and rotation — the number drops to 5,472,730,538, or roughly 5.47 billion. This set was enumerated in 2006 by Ed Russell and Frazer Jarvis.

Minimum Number of Clues

After years of mathematical debate, it was proven in 2013 that a Sudoku puzzle requires at least 17 clues to have a unique solution. No valid puzzle with 16 or fewer clues exists. The proof, performed by Gary McGuire and a team at University College Dublin, used exhaustive search pruning and required millions of CPU hours.

Our easiest puzzles start at ~40 clues. Our Extreme level generates puzzles with as few as 20 clues — close to the theoretical minimum while remaining human-solvable.

Average Solve Times by Difficulty

Solve times vary widely by individual skill, but these are typical ranges for experienced players:

  • Easy — 3 to 8 minutes
  • Medium — 7 to 20 minutes
  • Hard — 15 to 45 minutes
  • Expert — 30 to 120 minutes
  • Master — 60 to 180 minutes
  • Extreme — 90 minutes and up

World championship solvers complete easy puzzles in under 1 minute. The current world record for a classic 9×9 Sudoku stands at approximately 50 seconds, set by Wang Shiyao of China at the 2023 World Sudoku Championship.

Global Reach

Sudoku is played daily by an estimated 200+ million people worldwide. The World Puzzle Federation sanctions international competitions in over 30 countries. The first World Sudoku Championship was held in Lucca, Italy in 2006; the event now rotates internationally each year and includes solo and team categories across multiple puzzle types.