Sudoku SE Rating Calculator - Sudoku SE Rating Calculator
Measure the difficulty of sudoku puzzles and learn their SE (Sudoku Explainer) rating - Analyze Sudoku puzzle difficulty with our free SE Rating tool using Sudoku Explainer algorithm
The SE (Sudoku Explainer) Rating is the gold standard for scientifically measuring Sudoku difficulty. While many websites mislead users by labeling puzzles based on the count of given numbers (clues), real difficulty comes from logical complexity. **At Ozerlyn.com, we set a new standard:** Every single puzzle in our collection is algorithmically analyzed using the SE system to guarantee 100% accurate difficulty calibration.
Beginner (SE 1.0 - 2.5): Pure logic without notes. Solvable using 'Hidden Singles' (1.0-1.5) and 'Direct Pointing'. Perfect for learning the mechanics of row, column, and box scanning.
Intermediate (SE 2.6 - 5.5): The realm of pattern recognition. Requires pencil marks. Techniques include 'Naked Pairs/Triples' (3.0), 'Hidden Pairs' (3.4), and intersection locks. This is where casual solving turns into a mental workout.
Advanced (SE 5.6 - 8.3): Strictly logic-based but highly complex. Mandatory knowledge of 'X-Wing' (3.2+), 'Swordfish' (5.0), 'XY-Wing' (4.4+), and 'Simple Chains'. These puzzles require spotting subtle connections across the whole grid.
Master Class (SE 8.4+): The frontier of human capability. Solvable only with 'Dynamic Forcing Chains' (8.4+), 'Nishio', and 'Cell Forcing'. These puzzles are mathematically crafted to test the absolute limits of logical deduction.
At Ozerlyn.com, we believe in transparency. Our Difficulty Calculator doesn't just guess; it reverse-engineers the puzzle. It runs thousands of logical checks, starting from beginner techniques and moving to expert strategies, exactly as a human master would. It identifies the precise moment the puzzle fights back.
SE Rating Breakdown (Technique vs. Score)
SE 1.0 - 2.3 Singles & Intersections: The foundational moves. If you can count to 9, you can solve these.
SE 2.6 - 3.4 Subsets (Pairs/Triples): Finding constrained groups of numbers that lock each other int.
SE 3.5 - 5.2 Fish Patterns (X-Wing, Swordfish): Using rectangular symmetry to eliminate candidates.
SE 5.6 - 7.5 Single Digit Chains (Wings): Following the logical implication of a number across the board.
SE 8.0 - 11.9 Forcing Chains & Nets: 'If this is 5, then that is 6...' - complex dependency trees.
Trust the Score: Because Ozerlyn verifies every puzzle, a 3.0 is always a 3.0. No surprises, just pure logic.
SE (Sudoku Explainer) Rating — Complete Guide to Sudoku Difficulty
This page explains the SE Rating (Sudoku Explainer Rating) in practical terms so you can read Sudoku difficulty accurately, select the right level, and track your progress. You'll find the origin of SE, clear score bands, real examples, common mistakes, a training plan, and printable Sudoku PDFs with solutions for targeted practice. Printable Sudoku PDFs
What Is SE Rating & Where Did It Come From?
SE Rating (Sudoku Explainer Rating) is a logic-based metric introduced by the developer known as gsf, author of the open Sudoku Explainer program. Rather than judging a puzzle by clue count, SE evaluates the solution path step by step and identifies the most demanding move needed. The final score reflects the hardest technique required (e.g., Singles, Locked Candidates, X-Wing, Swordfish, chains, forcing nets). Because it models human reasoning instead of brute force, SE is widely used to compare relative difficulty across large sets of Sudokus.
In practice, SE helps solvers and editors: creators can grade and publish balanced sets; teachers can assign appropriate homework; and players can filter to a comfortable level or progressively climb the ladder. Many modern generators use SE-inspired grading so that puzzles remain human-solvable without guessing.
SE Difficulty Bands (Practical Ranges)
Labels vary by site, but these ranges offer a reliable rule of thumb. Aim for a band, not an exact number.
Beginner
0.0 – 1.5
Naked / Hidden Singles; almost all progress from basic eliminations. Ideal for learning notation and scanning.
Easy
1.6 – 3.0
Locked Candidates, simple interactions between row/column/box. Still smooth once you mark candidates.
Medium
3.1 – 5.0
X-Wing, Swordfish and similar patterns; you'll need structured candidate marking and deliberate scans.
Hard
5.1 – 8.0
Advanced chains, coloring, subset reasoning. Great for breaking standstills without guessing.
Expert
8.1 – 12.0+
Forcing nets and multi-step composite logic. Time-intensive but satisfying for dedicated solvers.
Remember: SE measures required logic, not minutes. A Medium puzzle might still take longer than a Hard one if you're unfamiliar with a specific pattern.
How an SE Score Is Produced (Worked Example)
Suppose the first dozen moves are Singles. The grid locks; you identify a Locked Candidates elimination (≈ SE 2.x). Progress halts again until an X-Wing removes a candidate column-pair (≈ SE 4.x). The remainder falls to Singles and simple pairs. Because the most demanding step was X-Wing, the puzzle reports around SE ≈ 4.x (Medium band). Editors like this because a single, clear 'ceiling technique' defines a consistent difficulty.
Reading & Using SE Rating Effectively
Target a range: Train in a 0.5–1.5 window (e.g., 3.5–4.5) until you're comfortable, then raise the band.
SE ≠ speed: It reflects logic depth, not solve time. Time improves as patterns become familiar.
No guessing: SE models human logic; backtracking doesn't reduce the score. If you have to guess, revisit candidate notes.
Annotate consistently: Use corner notes for candidates; reserve center notes for placed digits to reduce eye strain.
Print to focus: Paper solving reduces distractions and makes spotting fish patterns and chains easier.
Two-Week Skill Plan (SE-Driven)
Days
Target SE
Focus Technique
Daily Volume
1–2
1.6–2.8
Locked Candidates; row/column scanning
3 light puzzles
3–4
2.8–3.8
Naked/Hidden pairs & triples
2–3 puzzles
5–7
3.8–5.0
X-Wing/Swordfish identification via candidate grids
2 puzzles + review
8–10
5.1–6.5
Coloring concepts, short chains
1–2 puzzles, detailed notes
11–14
6.5+
Chain extension; clean notation; error recovery
1 puzzle + post-mortem
Track your average SE per day and highlight the technique that stalled you. Improvement shows up first as fewer stalls, then as faster recognition.
Printing & Practice Tips
Save before you print: keep a PDF archive by band; revisit the same SE later to verify progress.
Paper & pencil: 20–24 lb paper with a sharp pencil/eraser makes candidate work clean and readable.
Separate solutions: print answers on a final page to avoid accidental peeking.
Consistent grid: use large cells for candidate-heavy bands (5.0+); small cells for quick warm-ups.
Mini Glossary (Techniques Seen in SE)
Locked Candidates
If a candidate in a box appears only in one row/column, eliminate it from the rest of that row/column outside the box.
X-Wing
A 2×2 pattern across rows/columns that allows eliminating a candidate from the same columns/rows elsewhere.
Swordfish
A 3-row/3-column generalization of X-Wing; rarer but powerful for mid-high SE puzzles.
Coloring / Chains
Track implications across candidates; contradictions eliminate colors; confirmations place digits.
SE Rating — Short FAQ
What is SE Rating?
A difficulty index from 0 to 12+ based on the hardest human-logic technique required to solve a Sudoku.
Who created it?
The system originates from gsf, author of the open Sudoku Explainer tool widely referenced by the Sudoku community.
Does SE correlate with time?
Not directly. SE measures required logic, not minutes. It's excellent for relative comparisons between puzzles.
Can I use it for free?
Yes. Generate by level on Ozerlyn Sudoku and print Sudoku PDFs with solutions.
Ozerlyn Games - Free Online Sudoku & Brain Training Games | Ozerlyn Games - Best Online Puzzle Games