MLB Run Line by Month: When Do Teams Win by 2+ Runs?
One-run games barely change from April to October. The better team's run line, though, looks stronger once August arrives.
Written by Aoi MatsumotoMLB Picks & Parlays specialist
- Sport
- Baseball
- Question
- Does the month of the MLB season change how often games are decided by one run, and how often the home team or the better team covers −1.5?
- Sample
- MLB regular season 2000-2025 excluding the shortened 2020 season; 60,450 nine-inning games
- games decided by one run28.3%
- better team covered −1.541.4%
- better team −1.5 in September/October42.9%
- 9-inning games analysed60,450
Every spring I hear the same idea: early-season baseball is sloppy and close, and late-season baseball is where good teams pull away. I wanted to test that against the run line, because −1.5 is simply a question about margins. This study covers 60,450 nine-inning regular-season games from 2000 to 2025, with 2020 left out. It asks whether the month changes how often games finish by one run, and how often the home side or the better team wins by two or more.
The short answer is that the month barely moves one-run games, which sit at 28.3% overall. It does seem to matter for the better team on the run line, which covered −1.5 in 41.4% of games across the season and 42.9% in September/October. Home teams hardly shift at all. I treat this as background when I write my free MLB predictions page, never as a stand-alone reason to bet.
Window 1Winning margins hold remarkably steady from April to October
This stacked chart splits every game into one-run results, two-to-three-run results and margins of four or more. Overall, 28.3% were one-run games and 39.3% were decided by four or more. One-run games peaked in May at 29.0% and bottomed out in August at 27.8%.
The one shape I notice is in the middle band. Margins of two or three runs made up 32.7% of March/April games but 31.8% of September/October games, while the one-run share edges up to 28.8% at the back end. That is a slight squeeze toward the extremes late in the year, nothing dramatic.
View the data: final margin by month
| 1 run | 2-3 runs | 4+ runs | |
|---|---|---|---|
| Mar/Apr | 28.3% | 32.7% | 39.0% |
| May | 29.0% | 32.1% | 38.9% |
| Jun | 27.9% | 32.7% | 39.4% |
| Jul | 28.1% | 32.5% | 39.4% |
| Aug | 27.8% | 32.5% | 39.7% |
| Sep/Oct | 28.8% | 31.8% | 39.4% |
For a bettor, this means the value of +1.5 shouldn't drift much by month. If anyone tells you April is full of coin-flip games, the data says March/April sits at 28.3%, exactly the season-wide figure.
Window 2Day games run slightly tighter than night games most months
Splitting by start time adds a second calendar layer. In March/April, 29.1% of day games and 27.8% of night games were one-run games, and in July the split was 29.2% against 27.5%. May has the highest day-game reading on the chart at 29.9%.
September/October flips the pattern, with 28.4% of day games against 29.0% at night. I wouldn't build a theory on one flip, but I suspect it reflects late-season night games carrying more weight in the standings and bullpens being managed more carefully.
View the data: one-run games by month, day vs night
| Day games | Night games | |
|---|---|---|
| Mar/Apr | 29.1% | 27.8% |
| May | 29.9% | 28.6% |
| Jun | 28.3% | 27.7% |
| Jul | 29.2% | 27.5% |
| Aug | 28.0% | 27.8% |
| Sep/Oct | 28.4% | 29.0% |
My personal read is that day-game +1.5 deserves a slightly closer look early and mid-season, especially on getaway days when regulars are rested. Still, these gaps are small, and the starting matchup and bullpen workload matter far more.
Window 3The better team's run line edge arrives in August
This diverging chart shows each month against the all-month rate, for the home team and the better-record team laying −1.5. The better team sits below its average from March/April through July, with May the weakest at a little over a point below, then swings to 1.4 points above in August and +1.5 in September/October.
Home teams tell a flatter story: −0.6 points in March/April, 0.8 above in July and −0.4 in September/October. Part of the reason home −1.5 stays low everywhere is the walk-off, because a home team winning in the bottom of the ninth stops at the winning run.
View the data: run line −1.5 cover vs the all-month rate
| Home team −1.5 | Better team −1.5 | |
|---|---|---|
| Mar/Apr | −0.6% | −0.6% |
| May | 0.0% | −1.1% |
| Jun | +0.3% | −0.9% |
| Jul | +0.8% | −0.5% |
| Aug | +0.2% | +1.4% |
| Sep/Oct | −0.4% | +1.5% |
Why might the better team pull away late? My guess is that by August rosters have been reshaped at the trade deadline and weaker clubs start giving innings to younger arms, so the gap between strong and weak sides widens on the field.
Window 4Fair odds for the better team shorten from +148 to +133
The table puts the raw rates beside fair prices, which are simply one divided by the observed cover rate with no margin. Across all months the better team covered 41.4%, a fair price of +142. May is the longest at +148 and September/October the shortest at +133, with August close behind at +134.
Now the caveat I take most seriously: each month carries a 95% range of ±0.9 points on the one-run rate, and the monthly swings are of a similar size. The August and September/October readings are the most interesting in the file, but they are tendencies across many seasons, not a promise about any given week.
| Month | Games | 1-run | 95% range | Home −1.5 | Better −1.5 | Fair better −1.5 |
|---|---|---|---|---|---|---|
| Mar/Apr | 9,445 | 28.3% | ±0.9 | 35.9% | 40.8% | +145 |
| May | 10,405 | 29.0% | ±0.9 | 36.5% | 40.3% | +148 |
| Jun | 9,996 | 27.9% | ±0.9 | 36.8% | 40.5% | +147 |
| Jul | 9,576 | 28.1% | ±0.9 | 37.3% | 40.9% | +144 |
| Aug | 10,496 | 27.8% | ±0.9 | 36.7% | 42.8% | +134 |
| Sep/Oct | 10,532 | 28.8% | ±0.9 | 36.1% | 42.9% | +133 |
| All months | 60,450 | 28.3% | ±0.4 | 36.5% | 41.4% | +142 |
Fair odds = 1 / observed frequency, shown as American odds with no margin.
In practice I compare the market's −1.5 price on a clearly stronger side with these fair numbers. Late in the year, a price near +142 for a strong favourite on the run line interests me more than the same price in May, provided the pitching matchup agrees.
Best window
- Don't overrate April margins
Treat early-season +1.5 like any other month. March/April produced 28.3% one-run games, the same as the full-season rate.
- Revisit favourites after the deadline
The better team covered −1.5 at 42.8% in August and 42.9% in September/October, against 40.3% in May. That is the window where I give strong sides on the run line a second look.
- Discount home −1.5 year-round
Home teams covered only 36.5% overall and never above 37.3% in any month, partly because walk-offs cap the margin. Don't accept a short price on it at any point in the calendar.
Questions bettors ask
How often are MLB games decided by one run?
In 60,450 nine-inning games from 2000 to 2025, excluding 2020, 28.3% were decided by one run. The monthly figure ranged from 27.8% in August to 29.0% in May.
What is a fair price for the better team on the −1.5 run line?
Across all months the better-record team covered 41.4%, a fair price of +142 with no margin. That shortens to +133 in September/October and lengthens to +148 in May.
Do home teams cover the run line more often at certain points of the season?
Barely. Home −1.5 covered in 36.5% of all games, ranging only from 35.9% to 37.3% by month, with walk-off wins holding the rate down.
I'm Aoi Matsumoto, and I write the MLB picks and parlays at fixedmatches.vip — a sport where pitching matchups and patience beat everything else.
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