Difficulty overview
Difficulty ratings of classic sudoku from different sources can vary widely, making it hard to know what to expect. I have tried to align my classifications with commonly accepted standards, but there is no one 'right' system. To make it easier for you to find what you're looking for, in addition to free samples here is the detailed breakdown of what is included at different levels.
Ratings table
The techniques in each level are cumulative, so each level may contain all the techniques from lower levels in addition to the new techniques at that level. Just because a technique is not listed at a certain level doesn't mean that technique might not still be useful in some puzzles - it just means there is technically a solution path that doesn't need it. Everyone solves differently and that's part of the fun.
Note that the number of givens is often less important than you might think! Within the beginner/easy levels, the required techniques are mainly the same and the difference comes from the number of givens. However, from Medium I and above, difficulty is mainly determined by the techniques needed and the way they are sequenced in the puzzle, so the number of givens tend to fall in the same ranges.
|
Level |
Stars |
Techniques |
Givens |
|---|---|---|---|
|
Beginner |
1/2 |
hidden single (box), full house |
42-50 |
|
Easy I |
1 |
same as beginner |
35-41 |
|
Easy II |
2 |
+ hidden single (row/column) |
28-34 |
|
Medium I |
3 |
+ pointing, hidden pair |
21-30 |
|
Medium II |
4 |
+ hidden triplet, naked single |
21-30 |
|
Hard I |
5 |
+ claiming, naked pair, naked triplet, X-wing |
21-30 |
|
Hard II |
6 |
+ swordfish, turbot fish, skyscraper, two string kite |
21-30 |
|
Expert I |
7 |
+ XY-wing, XYZ-wing, W-wing, unique rectangle (types 1-4) |
21-30 |
|
Expert II |
8 |
+ naked quad, hidden quad, jellyfish, BUG type 1 |
21-30 |
|
Diabolical I+II |
9-10 |
+ forcing chain, forcing X-chain, aligned pair/triplet exclusion, region/cell forcing chains, Nishio, bidirectional Y-cycle |
21-30 |
