Tennis Elo Win Probability Calculator
Estimate each player’s chance of winning a match from their Elo ratings using the standard logistic Elo expected-score formula.
How it works
P(A beats B) = 1 ÷ (1 + 10^((RatingB − RatingA) ÷ 400))
Elo turns a rating difference into a win probability with a logistic curve: equal ratings give a 50/50 match, and every 400-point gap multiplies the odds by ten. A 100-point edge is worth about 64%, and a 200-point edge about 76%. The same formula drives tennis Elo systems, chess and countless other rating models, which is why it travels so well between sports.
Worked example
For a 2000-rated player against an 1800-rated player: P = 1 ÷ (1 + 10^((1800 − 2000)/400)) = 1 ÷ (1 + 10^−0.5) = 1 ÷ 1.316 = 0.760, so Player A wins about 76% of the time.
Sources: Elo rating system — Wikipedia
Frequently asked questions
What does a 400-point Elo gap mean?
A 400-point difference gives the stronger player about a 91% win probability — the odds shift by a factor of ten for every 400 points, which is the constant baked into the divisor.
Does this predict the score or just the winner?
Only the probability that a given player wins the match. It says nothing about sets or games, and it assumes a single head-to-head with no surface or fatigue adjustments.
Where do tennis Elo ratings come from?
They are built by starting every player near 1500 and updating after each match based on the result versus this expected probability. Surface-specific (clay/grass/hard) Elo variants are common in tennis analytics.
Related calculators
This calculator is for educational purposes. Double-check important results before acting on them.