One of the defining characteristics of baseball betting is how frequently games are decided by extremely small margins. Because most MLB games do not involve point spreads, sportsbooks use the runline (-1.5 runs) to create a handicap market.
Understanding how often games finish with narrow margins helps explain why the runline exists and how it affects betting strategy.
To examine this, we analyzed all MLB games played since 2004.
How Many MLB Games Are Decided By One Run?
Across the dataset of 52,697 games, exactly 14,968 games were decided by one run.
Games decided by exactly one run: 14,968
Percentage of total games: 28.4%
This means more than one out of every four MLB games ends with a one-run margin.
This high frequency is one of the main reasons sportsbooks offer runline betting options.
Favorites In One-Run Games
Next we looked at how betting favorites perform in games that ultimately end with a one-run margin.
SU: 8,200–6,410
Win Rate: 56.1%
ROI: -5.7%
Profit/Loss: -$124,725
Favorites win slightly more than half of these games, but the betting results show that favorites struggle to produce value in tight contests.
Because favorites must often lay expensive moneyline prices, close games tend to erode profitability.
Why One-Run Games Matter For Bettors
One-run games are particularly important for several reasons.
Runline Strategy
Because favorites must win by two or more runs to cover a standard runline bet, the high frequency of one-run games often benefits underdogs on the +1.5 runline.
Bullpen Variance
Late-game bullpen performance can dramatically impact final margins. A team leading by multiple runs may allow a late run that reduces the margin to one.
Strategic Decisions
Managers frequently adjust their strategy when leading late in games, prioritizing pitcher health and defensive matchups rather than maximizing run differential.
Key Takeaways
• 28.4% of MLB games are decided by exactly one run
• Favorites win about 56% of one-run games
• However, betting favorites in these games produces negative ROI
The high frequency of close games helps explain why runline betting exists in baseball markets.
