📊 Win Probability Calculator
Enter two ratings and see each player's expected chance of winning, computed from the logistic ELO curve that many rating ladders use.
📊 Expected Win Probability
Probabilities come from the logistic ELO curve: a 400-point edge means about a 91% chance to win. These are long-run expectations across many matches, not a guarantee for any single game.
What is a Win Probability Calculator?
It converts the rating gap between two players into a head-to-head win percentage for each of them. The same logistic curve that ELO uses to set expected scores tells you how often the favourite should win — 64% at a 100-point edge, about 91% at 400 — so you can read a match-up at a glance.
Use it to size up a draw before a tournament, to explain why a seeded player is expected to win but is far from certain, or to set fair expectations for a coaching group. Pair it with the rating and handicap calculators to see both the odds and the points a fair game would need.
❓ Frequently Asked Questions
How do you turn a rating difference into a win probability?
With the logistic ELO curve. The favourite's chance of winning is 1 / (1 + 10^((underdog rating − favourite rating) / 400)). The two players' percentages always add up to 100, because ELO folds the small chance of a draw into the expected score.
What does a 100-point rating gap mean in practice?
About 64% for the higher-rated player. A 200-point gap is roughly 76%, and a 400-point gap is about 91%. Each extra 100 points matters less the bigger the gap already is: the curve flattens as it nears 100%.
Are these odds a guarantee for one match?
No. They are long-run expectations across many matches between players of those ratings. On any given day form, style match-ups, and nerves can override the numbers — that is exactly why upsets happen and why the underdog still has a real chance.
Can I use this for any rating system?
Only for ratings built on ELO's 400-point logistic scale, as many club and online ladders are. Official systems such as USATT's work from their own published tables rather than this curve, so read the percentages as generic ELO odds, not an official prediction.