SCIENCE24 - The Science of Baseball's Home Run

There are more and more statistics used in calling Major League Baseball (MLB) games today, including those that measure the efficiency of the teams and the players, almost overwhelming the broadcast.  This is particularly true for describing home runs, where it is common to immediately state the exit velocity and the launch angle, followed by the estimated home run distance, and endless analysis. 

Home runs have always been fascinating to the baseball fan.  There are two aspects of home runs that are particularly fascinating to me:  1) What are the factors that determine home run distance and how do they work, i.e., what is the science of the home run, and 2) What is all the ruckus about torpedo bats, that are supposed to increase a batter’s home run proficiency?

I’m going to approach this in two parts.  This blog will be Part 1 and cover the science of the home run including key factors, and how home run distance is measured today.  My next blog, Part 2, will expand on the role of the baseball bat in hitting home runs, and address the properties of the torpedo bat.  I will mostly be talking about MLB and the wooden bats they use exclusively.

I will list my primary sources at the end.

 

Introduction

The concept of a home run in baseball evolved over time, initially referring to a batter circling all the bases after hitting the ball without being put out, often involving inside-the-park runs.  (In the early days - pre-1870s - baseball fields often had large, open, irregular outfields, making inside-the-park home runs more common.  A batter could run around the bases before the ball could be thrown in, resulting in a home run.  As ballparks became more defined and outfield fences or walls were built, the concept of a home run shifted towards hitting the ball over the outfield fence or wall, and there were fewer inside-the-park home runs.  After World War I, the baseball itself changed, becoming “livelier” due to improvements in materials and manufacturing.  This led to a significant increase in the number of home runs hit. 

Just to be clear, I’m going to talking about home runs that occur, when a batter hits a fair ball and scores on the play without being put out or without benefit of an error.  In almost every instance of a home run in MLB today, a batter hits the ball in the air over the outfield fence or wall in fair territory.

Home run distance is the linear distance from home plate to the point where the ball lands, typically recorded in feet.  When a batted ball hits a stadium artifact, like a high wall or sign, the home run distance is not the actual distance the ball traveled, but instead the projected home run distance, i.e., how far the ball would have traveled if it hadn't been interrupted by the obstruction.

The science of hitting a home run in baseball involves a complex interplay of physics, aerodynamics, and even the environment.  Here's a summary of the science behind home runs and a breakdown of the key factors that are involved.

 

Exit Velocity, Launch Angle, and Flight Time

Exit Velocity. This refers to how fast the ball leaves the bat after impact.  Higher exit velocity generally leads to a longer hit.  Factors that influence exit velocity include how fast the pitcher throws the ball, how fast the batter swings (bat speed), what particular wood the bat is made of, and the point of contact on the bat.

Launch Angle. The vertical angle at which the ball leaves the bat significantly impacts how far it travels.  In a vacuum, the optimal launch angle would be 45 degrees.  However, taking into account the mitigating factors discussed below, the optimal launch angle, is typically between 25-35 degrees for power hitters, allowing the ball to achieve the greatest distance.

Key factors in determining the distance of a home run.

 

Flight Time. The duration that the ball is in the air, can affect how wind and other environmental factors influence its path.

 

Composition and Physics of Bats

Bat Composition. In MLB, the required wooden bats must be a single piece of solid wood.  They are usually made of a hard wood such as maple, birch, or ash (hard woods transfer more energy to the baseball upon impact than softer woods) for increased exit velocity.  Traditionally they are made with ash because these bats are flexible and lightweight with an open grain structure.

The "Sweet Spot" and Bat Vibration. The sweet spot on a bat is the area where the most energy is transferred to the ball, minimizing vibration and maximizing power.  When the ball hits this area, it deforms the bat slightly, and the bat recoils, propelling the ball forward with maximum force.  When the ball hits the bat outside the sweet spot, the bat can vibrate, absorbing some of the energy that could have been transferred to the ball.  When a ball is hit on the sweet spot, it feels solid and powerful to the batter, with the ball traveling a greater distance. 

While the exact location of the sweet spot can vary depending on the bat's length, weight, and design, it's typically found roughly 5 to 7 inches from the barrel's end.  You can find the sweet spot by tapping different parts of the barrel with a ball while holding the bat with a loose grip near the handle.  The area with the least vibration is the sweet spot. 

Profile of a standard wooden bat.

 I’ll have more about the composition and physics of bats in Part 2.

 

Spin Rate

When a baseball is hit with backspin, the air flowing over the ball moves faster than the air flowing over the bottom of the ball.  This creates higher air pressure below the ball and produces an upward “lift” effect called the Magnus force, counteracting gravity, helping the ball stay in the air longer, and increasing the distance traveled.   Trying to achieve backspin is why MLB batters attempt to impact the ball on its lower half with an upward bat trajectory.

The Magnus force, created by backspin on a batted ball, produces longer home runs.

Research suggests an optimal spin rate for maximizing distance of around 1500-2500 rpm, while excessive spin (over 2500-3000 rpm) can lead to diminishing returns.  Too much spin causes increased drag on the ball, partially cancelling the lift generated.  The optimal spin rate is influenced by environmental factors that affect air density, like altitude and temperature.   

Topspin has the opposite effect of backspin, increasing air resistance and producing a downward force, that makes the ball drop faster and travel a shorter distance. 

Effect of spin rate on a nominal 350-foot home run.

Air Resistance:

Air resistance, also known as drag, is a major factor in limiting the distance a baseball can travel.  Drag slows down the ball, causing it to reach a lower height and shorter horizontal distance than it would in a vacuum.  (A fly ball that might travel around 700 feet in a vacuum would only carry about 400 feet with air resistance.)

Example of the effect of air temperature on home run distance. Over the temperature range shown, the horizonal distance varies about 25 feet.

Air resistance is affected by altitude, temperature, and humidity.  At higher altitudes and temperatures, air density is lower, resulting in less drag and allowing the ball to travel further.  Humid air is less dense than dry air, meaning a baseball will experience less air resistance and travel farther in humid conditions.

In general, cool and dry conditions, compared to hot and humid conditions, can make a difference of 20-30 feet in home run distance.

Lower air resistance at Coors Field in Denver (mile high altitude) is the reason home runs travel about 5% farther than at near sea-level ball parks. 

 

Wind

Wind is a very complex issue within a baseball stadium.  It swirls around the stadium in difficult to predict, chaotic patterns.  Small changes in wind speed or direction can create large changes in the local wind effects at any given point within the park, making the effect of wind difficult to account for.

A tailwind can significantly increase home run distance, while a headwind can decrease it. 

Example of wind effect on home run distance.  The 20-mph wind difference shown produces a distance variation of about 75 feet.

Ballpark Playing Field Dimensions and Obstructions

Each MLB ballpark has unique playing field dimensions, making some parks more conducive to home runs than others.  Looking across all MLB ballparks, the figure below shows a “composite” of the minimum and maximum distances from home plate to the outfield fence or wall.

Mash-up of different MLB ballpark shortest and longest playing field dimensions, illustrating significant differences in home run opportunities.

There is no standard height for outfield fences or walls in MLB ballparks, and they vary considerably, even within the same stadium.  Some fences or walls are relatively short (around 4-8 feet), while others are quite tall, like the Green Monster wall at Fenway Park, which is 37 feet high. 

Also, each ball park has its own set of artifacts or obstructions that could interfere with the flight of a home run ball.  These include seats in the stands, upper deck perturbances, scoreboards, signs, etc., making it harder to estimate the projected home run distance.

 

Calculating Home Run Distance

Traditional Methods. Historically, the distance of a home run was estimated through visual approximations or basic calculations.  This often involved measuring straight-line distances from home plate to the landing spot of the ball, but these methods lacked precision.

Two primary techniques were utilized:

1.    Eyeball Estimation: In the early days of baseball, the distance was often gauged by spectators and commentators, who would estimate how far the ball had traveled based on their view of the field.

2.       Architectural Mapping: Over time, stadiums were mapped with precise measurements of distances to various features. These maps allowed for more accurate estimations of home run distances based on the known dimensions of the field.

Advancements in Measurement Technology. The advent of statcast changed everything.  Statcast is an automated tool developed for MLB to track and analyze various aspects of the game, including pitches, hits, and player movements.  Statcast was introduced to all thirty MLB stadiums in 2015, and is licensed to ESPN.

Statcast is a sophisticated baseball tracking system that uses a combination of high-speed cameras and radar technology to gather detailed data on every aspect of the game. This data provides a wealth of information for teams, players, and fans. 

Each MLB organization now has an analytics team, using statcast data to gain a competitive advantage. This "arms race" of new data that is becoming available from statcast is a rapidly growing field within MLB teams in their "analytics" group.

In recent years, MLB has embraced statcast technology to enhance the accuracy of home run distance measurements.  In the statcast system today, multiple high-speed cameras are strategically placed around the ballpark to track the movement of the ball, players, and even the bat.  These cameras capture precise details about the ball's trajectory, launch angle, and spin rate.  Radar systems are used to track the speed and trajectory of the ball, particularly in relation to the pitcher and hitter. 

Statcast operates by capturing the ball's speed, launch angle, and trajectory immediately after it leaves the bat.  This information is processed to create a detailed model of the ball’s flight path, allowing for a more accurate calculation of the distance traveled.  Key factors influencing home run distance, accounted for in statcast's analysis, include exit velocity, launch angle, flight time, wind speed and direction, temperature, humidity, altitude, and stadium playing field dimensions and obstructions. 

Statcast combines these data points to generate a projected home run distance, accounting for variables that traditional methods could not measure.

Example of statcast analysis for a home run.

Conclusions

Using detailed data as statcast provides, MLB players have learned what the key factors are for producing home runs.  They study the data and train to improve their home run performance.  They watch videos of their hitting approach and swing, and use virtual reality simulations to make adjustments to improve home run success. 

An increasing emphasis on home runs in MLB, advanced technology to provide detailed analytical data, and ballplayers’ efforts to improve home run performance have had dramatic success.  See the chart below.

Historical increase in MLB home runs per year.

I’ll close with some home run data from 2025.  Here is a table summarizing the exit velocity and launch angles for the top 10 longest MLB home runs of the 2025 season so far, along with their respective distances:

Rank	Player	Distance (Feet)	Exit Velocity (mph)	Launch Angle (°)
1	Mike Trout	484	115.4	26
2	Byron Buxton	479	111.6	25
3	Logan O'Hoppe	470	108.1	34
4	Aaron Judge	469	117.9	31
5	Aaron Judge	468	115.0	30
6	Ryan McMahon	467	112.0	30
7	Ronald Acuña Jr.	467	115.5	23
8	Kyle Schwarber	466	109.3
9	Eugenio Suarez	466	111.7	25
10	Christian Yelich	465	110.6	25

 

“Every strike brings me closer to the next home run.” - Babe Ruth

 

Sources

My principal sources include: “How is Home Run Distance Measured?” platecrate.com; “Baseball bat” and “statcast,” Wikipedia.com; plus, numerous other online sources.  I am increasingly, and hopefully carefully, using Google’s AI/ChatGPT summaries of searches, including for this blog, “the science of home runs,” “calculating home run distance from exit velocity and launch angle,” “quantitatively, what are air resistance and spin rate impact on home run distance,” “what is the sweet spot on a baseball bat,” “how do people estimating home run distance consider the unique characteristics of each ball park construction,” “projectile range formula for baseball,” and “how does statcast work.”  These AI summaries directed me to numerous additional specific sources.