How your rating is calculated, what it means, and how to climb the ranks.
The ELO rating system is a method for calculating the relative skill of players, originally developed by physicist Arpad Elo for chess. Your rating is a single number that represents your strength — the higher the number, the stronger the player. When you win against a strong opponent, you gain more points. When you lose to a weaker opponent, you lose more points. Over time, your rating converges to a value that accurately reflects your skill level.
Sudoku Corner tracks two separate ratings for each player:
Resets every month at the start of a new season. All players return to 1200. This creates a fresh competitive cycle where everyone starts on equal footing. Your season ELO determines your position on the monthly leaderboard.
Never resets. This is your all-time rating that accumulates from every ranked match you've ever played. It represents your long-term skill progression and is shown on your profile.
Your ELO is tracked separately for each division. Playing Beginner matches only affects your Beginner rating, and so on. This means you can be a strong Expert player but still start fresh in Beginner if you haven't played it yet.
This system ensures that your rating in each difficulty tier reflects your actual skill at that level. A player who excels at Beginner puzzles won't automatically rank high in Expert — they need to prove themselves there too.
After each ranked match, the ELO change is calculated in three steps:
First, we calculate how likely each player is to win based on their current ratings. If two players have the same ELO, each has a 50% expected score. A 200-point difference gives the stronger player about 76% expected score.
The match result is expressed as a number: 1.0 for a win, 0.0 for a loss, and 0.5 for a draw.
The difference between your actual result and expected score, multiplied by the K-factor, gives your rating change.
The K-factor controls how much your rating can change in a single match. New players use a higher K-factor so their rating adjusts quickly to their true skill level. After gaining experience, the K-factor decreases for more stable ratings.
| Player Status | Games Played | K-Factor | Max Change Per Match |
|---|---|---|---|
| New Player | < 30 games | 40 | ±40 points |
| Established Player | ≥ 30 games | 20 | ±20 points |
Let's see how ELO changes work in practice. All examples assume both players are established (K=20).
Both have equal ratings, so the expected score is 50% for each player.
With equal ratings, the winner gains and loser loses the same amount: ±10 points.
Carlos is expected to win ~85% of the time. Diana only ~15%.
Key insight: When the favorite wins, only 3 points change — the system "expected" it. But when the underdog wins, 17 points change — the upset is rewarded heavily.
Eva is slightly stronger. Her expected score is ~64% vs Frank's ~36%.
Grace is new (K=40) so her rating changes faster. Henry is established (K=20).
With K=40, Grace's rating moves twice as fast as established players, helping her reach her true skill level quickly.
This table shows how the expected win probability changes based on the rating gap between two players:
| Rating Diff | Stronger Win% | Weaker Win% | If Stronger Wins | If Weaker Wins |
|---|---|---|---|---|
| Equal | 50% | 50% | +10 / -10 | +10 / -10 |
| +50 | 57% | 43% | +9 / -9 | +11 / -11 |
| +100 | 64% | 36% | +7 / -7 | +13 / -13 |
| +150 | 70% | 30% | +6 / -6 | +14 / -14 |
| +200 | 76% | 24% | +5 / -5 | +15 / -15 |
| +300 | 85% | 15% | +3 / -3 | +17 / -17 |
| +400 | 91% | 9% | +2 / -2 | +18 / -18 |
Values shown for established players (K=20). New players (K=40) see double the changes.
At the beginning of each month, a new season starts. All players' season ELO is reset to 1200 in every division. This creates a fresh competition every month with the following benefits:
Everyone starts equal each month, so even new players can compete for top spots.
Had a bad month? Season reset gives you a clean slate to prove yourself again.
Compete for top season rankings. Your season performance earns points toward the weekly leaderboard.
Your global (all-time) rating never resets, so your long-term progress is always preserved.
Your rating becomes more accurate with more games. The first 30 matches are calibration games with higher point swings.
Losing to someone rated 200+ above you costs very few points. But winning earns a massive reward.
Reaching max errors means automatic loss, regardless of progress. Each error also adds a time penalty.
Training matches don't affect your ELO. Use them to warm up and learn patterns risk-free.