What percentage of MLB games have a run in the first inning?

In the 2025 MLB regular season, 50.21% of games had at least one run scored in the first inning. Statr calculated that result from Retrosheet's game logs: 1,220 of 2,430 games had a run in either the top or bottom of the first.

The other 1,210 games—49.79%—had a scoreless first inning. This is a description of one completed season, not the probability for today's matchup or a demonstrated betting strategy.

The 2025 first-inning scoring results

Scope: MLB regular-season games in Retrosheet's 2025 game-log file, from March 18 through September 28, 2025. Postseason and spring-training games are not included. Calculation checked September 30, 2026.

What counts as a first-inning run?

A game counts as having a first-inning run if the visiting team scores in the top of the first, the home team scores in the bottom of the first, or both do.

Each game counts once. A 1–0 first inning and a 4–3 first inning both belong in the "at least one run" group. We are measuring the percentage of games with scoring, not the number of runs scored, the percentage of individual teams that scored, or the share of innings with a run.

How we calculated the percentage

We used the 2025 Retrosheet game-log archive. Its field guide identifies fields 20 and 21 as the visiting and home line scores.

For each game, we read the first-inning run total for both teams, added them together, and counted whether the result exceeded zero.

First-inning scoring percentage = games with at least one first-inning run ÷ games analyzed × 100.

For 2025: 1,220 ÷ 2,430 × 100 = 50.21%, rounded to two decimal places.

The checks found no duplicate game records or missing first-inning line scores in the file. We also verified that each team's complete line score summed to its recorded final run total. Doubleheader games were counted separately. Suspended games use the completed game record rather than being counted again on resumption.

What this means for NRFI and YRFI research

NRFI commonly means "no run first inning." YRFI commonly means "yes run first inning." For markets defined by either team scoring during the full first inning, the two groups above describe the corresponding historical scoring outcomes. Sportsbook settlement rules still govern actual wagers, including interrupted games and other exceptions.

The league-wide result is useful as background. It does not make every matchup a 50.21% proposition. Starting pitchers, the top of each lineup, player availability, the park, and conditions differ from game to game.

The price matters too. In a simple win-or-lose market, -110 requires a win rate above 52.38% to break even before any other costs. That is higher than the study's league-wide 50.21% scoring rate. Comparing these numbers illustrates why "it happens about half the time" is not enough to establish value. It is not a recommendation for either side.

Read the expected-value guide for the difference between an observed rate, an estimated probability, and a price-derived break-even threshold.

First inning is different from first five

An NRFI or YRFI question concerns the first inning. An F5 market covers five innings and can involve a moneyline, run line, total, or team total. A scoreless first inning can be followed by several scoring innings, so the results are not interchangeable. See our first-five betting guide.

Limits of this study

This analysis covers one season and gives every game equal weight. It does not adjust for pitchers, lineups, teams, parks, weather, or the odds offered at the time. It does not calculate returns from a betting strategy or estimate a probability for a future game.

The underlying records can be corrected by the data provider. Any later update to this study should identify the source version and rerun the count rather than changing the year in the headline.

Ask a matchup-specific question

Use the season baseline to frame better research: "What is different about these starting pitchers and the top of these lineups, and which current information is missing?"

Open Statr to explore the available context, or read how Statr uses data and explains uncertainty. First-inning coverage may be limited; a general matchup assessment is not a calibrated NRFI or YRFI forecast.

Data attribution: The information used here was obtained free of charge from and is copyrighted by Retrosheet. Interested parties may contact Retrosheet at www.retrosheet.org.

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