What is the break-even stolen base success rate?

It is the success probability at which a steal attempt neither adds nor subtracts expected runs. Using standard run-expectancy tables, stealing second with no outs sits near 70 to 75 percent, meaning you must succeed that often just to break even.

Why is being caught more costly than the advance is valuable?

A caught stealing removes the runner and adds an out, wiping out a chunk of run expectancy. The advance only nudges expectancy up by one base. Because the downside outweighs the upside, the break-even success rate is well above 50 percent.

Where do the run-expectancy numbers come from?

Run expectancy comes from league-wide play-by-play data that averages how many runs score from each of the 24 base-out states. The defaults here reflect a typical modern MLB table; you can substitute your league's own values.

How is the break-even formula derived?

Let gain be the run-expectancy rise on success and loss be the drop if caught. Setting expected change to zero gives break-even equals loss divided by gain plus loss. That single ratio captures the whole risk-reward trade-off.

Does this account for game situation?

It is built on average run expectancy, not win probability. In late, close games the win-probability break-even can be higher or lower. Use this for general strategy and adjust for score, inning, and the batter at the plate.

Baseball Stolen Base Break-Even Calculator

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Stealing a base is a bet: succeed and the runner advances, fail and the team loses both the runner and an out. This calculator finds the success rate at which that bet pays off, using run expectancy, the average runs scored from each base-out state.

How it works

Every steal attempt moves the team between run-expectancy states. Define the gain on success and the loss if caught, then solve for the success probability where the expected change is zero:

gain       = RE(success) - RE(now)
loss       = RE(now) - RE(caught)
break-even = loss / (gain + loss)

Because being caught removes the runner and adds an out, the loss is large relative to the gain, which pushes the break-even rate well above half.

Example and notes

With a typical MLB table, a runner on first with no outs has a run expectancy near 0.83. Stealing second cleanly raises it to about 1.07, a gain of roughly 0.24 runs. Getting caught drops it to about 0.24, a loss of roughly 0.59 runs. The break-even is 0.59 / (0.24 + 0.59), about 71 percent. So a runner who succeeds 75 percent of the time adds expected runs, while one at 65 percent is hurting the team. This model uses average run expectancy, not win probability, so in late, close games adjust for score and inning.