Stolen Base Percentage Calculator (SB%)

Background.

Stolen base percentage is the simplest question in baseball and one of the most consequential: of the times a runner tried to take a base, how often did he make it? The formula is SB ÷ (SB + CS) and nothing else goes into it. The Official Baseball Rules define both halves — Rule 9.07 credits a stolen base whenever a runner advances a base unaided by a hit, putout, error, force-out, fielder's choice, passed ball, wild pitch or balk, and Rule 9.07(h) charges a caught stealing when he is put out, or would have been put out by errorless play, trying to steal, advancing after a pick-off, or oversliding.

What makes the number matter is that a stolen base is worth much less than a caught stealing costs. FanGraphs sets the run value of a stolen base at +0.2 runs for every season, while the cost of being caught is roughly twice the value of an out plus a further 0.075 runs — a considerably larger number, because getting thrown out both removes a baserunner and burns an out. That asymmetry is why the rule of thumb is that a runner wants at least twice as many stolen bases as caught stealings before the running is helping at all, a success rate of about 66.7%. FanGraphs is careful to add that the exact figure moves with the run environment, and this page repeats that caveat rather than printing a single break-even number as though it were fixed.

This calculator gives the rate, the attempt and caught-stealing counts behind it, how far the runner sits from that 2-to-1 rule of thumb in both percentage points and steals, and a planner that answers the question a player or coach actually asks in mid-season: how many clean steals in a row would it take to get the number back where I want it? Every figure is checked against the league's own published rate — the 2025 lines used in the worked example reproduce MLB's published stolen base percentages exactly.

What is stolen base percentage calculator?

Stolen base percentage, usually written SB%, is a runner's success rate on stolen base attempts: stolen bases divided by stolen bases plus caught stealings. It is normally printed as a three-decimal rate in the same style as batting average, so a runner who is 44 for 56 shows .786. The two components are official scorer's judgements defined in Rule 9.07 of the Official Baseball Rules, and the definitions are narrower than casual usage suggests. A runner who advances on a wild pitch or a passed ball is not credited with a steal unless he was already moving before the pitch was delivered. A runner picked off first base who never breaks for second is charged with neither a stolen base nor a caught stealing — the play is scored a pick-off, and it disappears from SB% entirely. That last exclusion means SB% systematically flatters runners who are frequently picked off, and it is one reason modern baserunning metrics work from play-by-play data rather than from the two box-score columns. What SB% does capture, cleanly and without judgement calls about run environment, is the ratio a manager is actually deciding on when he sends a runner.

How to use this calculator.

1. 01Enter stolen bases and caught stealings straight from the box score or the season line. Both are scorer-recorded categories; do not reconstruct them from memory of individual plays.
2. 02Read the rate against the 2-to-1 gap rather than against a fixed threshold. Sitting above 66.7% means the running is more likely than not adding value; sitting below it means the caught stealings are probably eating the gains.
3. 03Look at the net steals figure alongside the percentage. A runner at 70% on ten attempts and a runner at 70% on a hundred are the same rate and completely different amounts of value.
4. 04Use the planner to size the hole. Because attempts already banked stay in the denominator forever, digging out of a bad start takes far more consecutive steals than most people guess.
5. 05Remember what the statistic cannot see: pick-offs where the runner never moved, steals of third versus steals of second, and the game situations in which the attempts were made. None of them enters SB%.

The formula.

The rate itself needs no explanation: successes over attempts. The interesting arithmetic is everything around it.

The 2-to-1 rule of thumb. FanGraphs publishes two run values for the running game: a stolen base is worth +0.2 runs in every season, and a caught stealing is worth −(2 × runs per out + 0.075). Because the value of an out is itself somewhere around a quarter of a run, the caught-stealing penalty lands around −0.45 runs and the ratio of cost to benefit lands a little above two to one. Setting 0.2 × SB equal to the caught-stealing cost × CS and solving gives a break-even success rate slightly above two-thirds, which is where the familiar guidance comes from. The gap output on this page measures distance from exactly 66.67%; the net steals output says the same thing as SB − 2 × CS, which is often the easier number to hold in your head.

The planner. To reach a target rate t after n further successful steals with no more caught stealings, you need (SB + n) ÷ (attempts + n) ≥ t. Multiplying out gives SB + n ≥ t × attempts + t × n, so n(1 − t) ≥ t × attempts − SB, and the smallest whole answer is n = ceil((t × attempts − SB) ÷ (1 − t)). The (1 − t) denominator is what makes high targets so expensive: at a target of 90% each successful steal buys a tenth of what it buys at a target of 50%. A target of exactly 100% is rejected, because that would divide by zero — once a caught stealing is on the record, no finite run of steals erases it.

One caveat the arithmetic cannot fix. Stolen base attempts are not evenly valuable. Stealing second with nobody out in a tie game and stealing third with two out are different decisions with different break-even rates, and neither the raw percentage nor the 2-to-1 shortcut distinguishes them.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Major League Baseball (2026). Official Baseball Rules, Rule 9.07 'Stolen Bases and Caught Stealing': 'The Official Scorer shall credit a stolen base to a runner whenever the runner advances one base unaided by a hit, a putout, an error, a force-out, a fielder's choice, a passed ball, a wild pitch or a balk'. Rule 9.07(a) covers the runner already in motion on a wild pitch or passed ball, Rule 9.07(h) defines caught stealing, and Rule 9.02(a)(9) and (18) make stolen bases and caught stealing box-score categories.
2. [2]MLB Advanced Media, Stats API — 2025 stolen-base leaders, including the league's own stolenBasePercentage field. Chandler Simpson is returned with stolenBases 44, caughtStealing 12 and stolenBasePercentage .786, and José Ramírez with 44, 7 and .863; both are reproduced exactly by this calculator as SB ÷ (SB + CS).
3. [3]FanGraphs Library, 'wSB'. Source of the run values quoted on this page — 'The run value of a stolen base is set at .2 runs for all seasons' and 'runCS = – (2 x RunsPerOut + 0.075)' — and of the break-even guidance used for the gap output: as a rule of thumb you want at least twice as many stolen bases as caught stealings, though that number bounces around based on the run environment.