Which stats actually matter for home run props?
How hard he hits it and at what angle, which Statcast rolls into barrel rate. Then how often he puts the ball in the air at all, who is pitching and from which side, where the game is being played, and how many times he comes to the plate. Barrel rate leads because it identifies the batted balls that have historically produced the most damage, which is the population home runs come out of.
A home run is four things happening at once. The ball has to be hit hard, hit in the air, hit at roughly the right angle, and it has to happen often enough across the game to show up on a 0.5 line.
Every statistic below is measuring one of those four. That is the whole framework, and it is more useful than a list.
How hard, and at what angle
These two only mean something together, which is the thing most explainers get wrong.
Exit velocity is how fast the ball leaves the bat. On its own it is not enough: a 108 mph ground ball is a hard out. Launch angle is the vertical angle it leaves at. Also not enough: a 25 degree pop-up at 70 mph is a lazy flyout.
Home runs live where high exit velocity meets a launch angle window somewhere in the twenties and thirties.
Barrel rate is the metric that combines them. MLB defines a barrel as a batted ball whose comparable hit types, in exit velocity and launch angle, have produced at least a .500 batting average and a 1.500 slugging percentage since Statcast went league-wide in 2015. Barrel rate is the share of a hitter’s batted balls that qualify.
Worth being precise about what that is and is not. A barrel is not defined as a home run, and barrel rate was not built to predict them specifically. It identifies the most damaging contact in the game, measured by batting average and slugging. Home runs are a large part of what that contact produces, which is why the metric is the natural starting point here, but a barrel can also be a double off the wall and a home run can come off a ball that never qualified.
One thing worth getting right, because it is misquoted constantly. The 98 mph figure is a minimum, not a cutoff you apply on its own. The window widens as exit velocity rises, and MLB publishes the shape of it:
| Exit velocity | Launch angles that qualify |
|---|---|
| 98 mph | 26 to 30 degrees |
| 99 mph | 25 to 31 degrees |
| 100 mph | 24 to 33 degrees |
| above 100 | another two to three degrees per mph, out to 116 |
So a ball at 100 mph qualifies across nine degrees where one at 98 qualifies across four. Treating the definition as a fixed rectangle instead of an expanding window produces a number wrong by a wide margin, and we know because we did it ourselves and had to rebuild two seasons of work on the corrected version.
Hard-hit rate, the share of batted balls at 95 mph or more, is the simpler version. Less precise, harder to fool yourself with, and available everywhere.
Whether he hits it in the air at all
A hitter can barrel the ball at an excellent rate and still not hit many home runs, because he does not put enough balls in the air for the rate to matter.
Fly-ball rate and ground-ball rate are the check. Home runs come off balls hit in the air, so a hitter with elite exit velocity and a 55 percent ground-ball rate is putting most of his best contact into the ground, where it cannot leave the park.
This is the most common way a hitter looks better on paper than the home run market says he is.
Pull rate belongs here too, because where a ball is hit interacts with the shape of the park it is hit in, and those shapes are not symmetrical.
Who is pitching
Handedness first. Most hitters have a real platoon split and some have an enormous one. A left-handed hitter facing a left-handed starter is in the harder version of his night, and power is where the split usually shows up before batting average does.
The pitcher’s own home run rate. Some pitchers give up hard contact in the air as a matter of style, not luck. The input our own board uses on the pitcher side of this market is home runs allowed per plate appearance, checked against a league mark of roughly 3.5 percent. That is what we actually look at, so it seemed more useful to tell you than to list every statistic that exists.
Ground-ball pitchers suppress this market directly. They are not allowing many balls in the air for anyone to hit out.
Where the game is
Parks change home runs, and they do it unevenly. Outfield dimensions are not symmetrical, so a park is not simply generous or stingy: it can favour balls hit to one field and punish the other, which means the same park treats two hitters in the same lineup differently depending on where they hit the ball.
We are going to leave it there rather than hand you a number. Our own park work has not cleared our internal bar for publication, and quoting a figure we have not blessed would be exactly the thing this site argues against. Park matters. We are not going to tell you it is worth precisely X.
Weather is a real influence on how far a ball carries. Our own testing did not support using it as a standalone selection rule, which is a narrower statement than saying it does not matter.
How many chances he gets
The one most guides skip entirely.
A home run prop is usually a 0.5 line, which means you are asking for at least one across the whole game. Four plate appearances is meaningfully more likely to produce one than three, and lineup position is most of what decides which he gets.
Batting leadoff means roughly one extra plate appearance every other game compared with batting seventh. On a market this binary, an extra chance is worth real money.
We estimate this on our board, and the limitation is worth stating: the live version has run biased high. It is an estimate, not a measurement.
The order to check them in, and why it is not a ranking
- Does he hit it hard and in the air? Barrel rate, then fly-ball rate to check the barrels have somewhere to go.
- Is tonight the good version of him? Handedness, then the pitcher’s home run rate.
- Does the park help this particular hitter? Pull direction against that fence.
- How many swings does he get? Lineup spot.
That sequence is a workflow, not a leaderboard. Each step changes what the next one means, which is why it runs in that order. It is not evidence that barrel rate outranks lineup position by some measurable factor, and we have not measured that.
The one ordering claim we will stand behind is a reasoned one rather than a measured one: barrel rate goes first because it identifies the most damaging contact in the game by construction, and home runs come out of that population. MLB defines the metric. Putting it at the front of this list is our inference, and if you disagree with that ordering nothing else on the page depends on it.
Where to see it
Every home run line on the Lab board sits next to the form, the matchup and the price, and today’s MLB player props carries the ones we selected with the book beside them.
The same four-question structure applies to the neighbouring market, where the answers come out differently: which stats matter for total bases props leads on contact quality and exposure rather than on barrels. And if you are not sure a home run line’s price is any good, overs vs unders on player props is the place to start.
What we are not claiming
No hit rate, ROI or edge figure for any home run model appears on this page, and none is implied. The barrel definition and its launch-angle windows are quoted from MLB’s glossary rather than from memory. The pitcher-side input and the plate appearance estimate are ours, described as we use them, including where the estimate is known to be biased. The park effect is named and deliberately not quantified, because our own measurement of it has not cleared publication.
Quick answers
What is barrel rate?
MLB defines a barrel as a batted ball whose comparable hit types, in exit velocity and launch angle, have produced at least a .500 batting average and a 1.500 slugging percentage since 2015. Barrel rate is the share of a hitter's batted balls that qualify. It identifies the most damaging contact rather than home runs specifically, and home runs are a large part of what that contact produces.
Is barrel rate a fixed 98 mph cutoff?
No, and this is widely misquoted. 98 mph is the minimum, and at that speed only launch angles between 26 and 30 degrees qualify. The window WIDENS as exit velocity climbs: 25 to 31 degrees at 99 mph, 24 to 33 at 100, and wider still above that.
Does exit velocity alone predict home runs?
Not on its own. A 108 mph ground ball is an out or a single. Exit velocity matters in combination with launch angle, which is exactly why barrel rate exists as a single number instead.
Do ballparks matter for home run props?
Yes. The same fly ball is a home run in one park and a flyout in another, and the effect differs by the direction the ball is hit. We have not published a number for how much it is worth, so treat it as a real factor without a price tag attached.
Want tonight's board?
The Lab prices every player prop on the slate, shows the form and the matchup behind each line, and posts a short card before first pitch. Every pick is graded in public afterwards, win or lose. It is free and there is nothing to sign up for.