How the Tennis probabilities are calculated
For every Tennis match, Babeth reads the odds of Pinnacle, the bookmaker known for the fairest odds on the market, removes the margin (the “power” method, which corrects the favourite-longshot bias), then blends them with the price on Betfair Exchange, one of the largest betting exchanges in the world (40%, only when the market is liquid enough). The result is an estimate of the real chance of each outcome — not a prediction.
These probabilities are recalculated every minute by the engine and published here every 5 minutes, right up to kick-off. Their accuracy is measured continuously on thousands of settled matches (Brier score, calibration) and published on the Results page. To find the mispriced odds on these matches at about forty bookmakers, you need a Proba Bet account; the trial is free.
Frequently asked questions
Are these probabilities predictions for Tennis?
No. A 60% probability means that, over a hundred comparable Tennis matches, the outcome happens about sixty times — and doesn't happen forty times. Babeth doesn't predict a score: she measures the real chance of each outcome, which tells you whether a price pays enough.
Why are the probabilities shown different from my bookmaker's?
Because the “implied” probability of a price contains the bookmaker's margin: add up the inverses of a match's odds and you always get more than 100%. Here the margin is removed, and the source is the bookmaker known as the fairest on the market rather than yours. When your bookmaker pays more than the fair odds shown here, you are holding a value bet.
How often are the Tennis probabilities updated?
The engine re-reads the reference odds every 60 seconds and this page is refreshed every 5 minutes, right up to kick-off. Tennis matches appear as soon as Pinnacle or Betfair Exchange price them, usually four days before kick-off.