| Very Easy | | (0.0-0.9) | | Can be solved quickly using elementary means. |
| Easy | | (1.0-1.9) | | Can be solved using elementary means. |
| Moderate | | (2.0-2.9) | | Usually can be solved using elementary means, but may take a while. |
| Hard | | (3.0-3.9) | | May require some techniques beyond simple scanning. |
| Very Hard | | (4.0-4.9) | | Requires somewhat advanced techniques. |
| Expert | | (5.0-5.9) | | For seasoned Sudoku players. |
| Fiendish | | (6.0-6.9) | | For Sudoku gurus only. |
| Diabolical | | (7.0-7.9) | | Very difficult to solve by hand, even for the gurus. |
| Serpentine | | (8.0-9.9) | | Only the most ambitious of Sudoku players should attempt these puzzles. |
| Ludicrous | | (10.0+) | | Not recommended for human solvers. |
