GameTicker is an experiment in real-time visualizations of baseball game win probability.

What is win probability?

Win probability represents the chance of a team winning at a specific situation in a baseball game.

How are win probabilities calculated?

First, the current game situation is compared to a run expectancy matrix (like this one) to find the probability that the batting team will score one, two, three, or more runs in the current half inning given the baserunner/outs situation following each event in the game. Then, each team's likely final run totals are calculated by considering the distribution of expected runs scored in the remaining innings of the game. The distribution of expected run totals are compared to generate a win probability for each team.

The run environment affects each step of this process. For example, a one-run lead is not as safe in a hitter-friendly park with the wind blowing out to centerfield than it is during a cool evening game at a pitcher-friendly park. At Gameticker, each game is associated with a custom run environment. These run environment estimates are mostly derived from team, league and park norms, but they also include adjustments for the home plate umpire and weather conditions.

Where can I learn more about win probability in baseball?

You can start here. I also recommend The Book.

Is it a good idea to sacrifice bunt?

It depends.

Where are the individual player statistics such as win probability added?

It's tempting to reduce win probability to individual player contributions. Mills and Mills constructed player win averages in 1970 and the idea has been reinvented many times since then.

You won't find such golden hammers here. I encourage you to enjoy win probability for what it is; a real-time description of a complex game state.

How can a team be losing and have a win probability greater than 50%?

The most likely explanation is that the team is only losing by one run and is in a situation where they will probably score more than one run in the inning (for example, if they have the bases loaded with no outs).

Are the win probability estimates live?

The win probability for each game will usually update about once every two minutes. If many other games are going on at the same time, updates may be less frequent.

Why can't I see the charts?

Please make sure you have javascript enabled on a modern web browser (for example, Firefox 3.0+, Safari 3.0+, Opera 9.5+ or Internet Explorer 6.0+)

I have more questions!

OK. Feel free to send me an e-mail at