Run Differential Projection Calculator
Project a baseball team’s full-season run differential and expected win total from its runs scored and allowed so far.
How it works
Projected differential = (runs scored − runs allowed) ÷ games played × season games · Projected wins ≈ season ÷ 2 + projected differential ÷ 10
Run differential is baseball’s cleanest signal of team quality, and it scales almost linearly with wins: a widely used rule of thumb is that every ten runs of differential is worth about one win above .500. Projecting the current per-game differential across the full schedule, then applying that rule, gives a quick expected win total that often beats a team’s record when close-game luck has skewed the standings.
Worked example
A team that has scored 300 and allowed 250 in 60 games is +50, or +0.83 per game. Over 162 games that projects to about +135, which under the ten-runs rule implies roughly 81 + 13.5 ≈ 95 wins.
Frequently asked questions
How accurate is the 10-runs-per-win rule?
It is a solid approximation for typical run environments. The Pythagorean formula is more precise, especially for teams at the extremes, but the ten-runs rule is easy to do in your head.
Why project run differential at all?
A team’s record early in the season is noisy, but its run differential stabilises faster and predicts the rest of the year better, so projecting it forecasts the final standings more reliably.
Does this replace Pythagorean expectation?
They complement each other. Use run differential for a quick linear projection and the Pythagorean calculator when you want a win percentage derived directly from runs scored and allowed.
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This calculator is for educational purposes. Double-check important results before acting on them.