What is Fly Ball Rate? Definition, Formula, and Example

Plain-English Definition

Fly ball rate, abbreviated FB%, is the share of a player's batted balls that are classified as fly balls. It is calculated for both hitters (how often they put the ball in the air) and pitchers (how often they induce fly balls). Along with ground ball rate, line drive rate, and pop-up rate, it is one of the four pillars of a batted-ball profile. A high FB% hitter lifts the ball; a high FB% pitcher pitches up in the zone or relies on a rising four-seamer. Modern hitting and pitching philosophies have diverged sharply on whether high FB% is good or bad.

How It's Calculated

The formula is:

FB% = Fly Balls ÷ (Ground Balls + Line Drives + Fly Balls + Pop Ups)

Or equivalently, FB% = Fly Balls ÷ Total Batted Balls in play. Home runs are typically counted as fly balls. A separate metric, HR/FB (home run per fly ball), measures what share of those fly balls leave the yard.

Batted-ball classification was historically done by official scorers; today Statcast uses launch angle to define categories more rigorously:

• Ground ball: launch angle < 10°
• Line drive: 10°–25°
• Fly ball: 25°–50°
• Pop-up: > 50°

The MLB league average FB% has hovered around 35–37% over the past decade, up from ~33% in the early 2010s as the launch angle revolution took hold.

Worked Example

In 2023, Joey Gallo posted one of the highest fly ball rates in the league at 53.2% — over half his contact went in the air. He paired it with a 27% HR/FB rate, meaning roughly one of every four fly balls became a home run. The trade-off: a sub-.180 batting average driven by pop-ups and weak fly outs.

On the pitching side, Justin Verlander has long run a fly ball rate near 40% thanks to his four-seam approach up in the zone, while sinkerballers like Framber Valdez sit closer to 25% FB and induce ground balls at well over 60% rates.

Why It Matters

Fly ball rate drives three downstream outcomes:

• Home run power. Only balls in the air leave the park. A hitter with a 25% FB% and elite exit velocity is leaving home runs on the table; the same hitter at 40% FB% taps that power.
• BABIP suppression. Fly balls have a low BABIP — around .120 league-wide — because they are caught more often than ground balls or liners. High-FB hitters therefore run lower batting averages.
• Park and ballpark factors. Fly ball pitchers in cavernous parks (Oakland Coliseum, Comerica) thrive; the same arms in Cincinnati or Coors get punished. Park factor interacts heavily with FB%.

Front offices use FB% to project HR ceiling for prospects with raw power and to flag pitchers whose ERA is held up by an unsustainably low HR/FB rate.

Limitations and Common Misconceptions

• High FB% is not automatically good for hitters. A hitter with weak contact and a high fly ball rate produces lazy outs to the warning track. FB% must be paired with hard-hit rate and exit velocity to mean power.
• Classification edges matter. A 24.9° launch angle is a line drive; a 25.1° is a fly ball. Cross-source disagreement on the same batted ball is common.
• HR/FB regresses heavily. A pitcher posting a 6% HR/FB rate is likely to regress toward the ~11% league average. xFIP is specifically built to neutralize this.
• Home runs distort the denominator. Some sources separate HR from fly balls; others bundle them. Always check the source.

Related Terms

• What is Ground Ball Rate?
• What is Launch Angle?
• What is Hard-Hit Rate?
• What is xFIP?
• What is Barrel Rate?

In Legends Deck

Legends Deck simulates every batted ball as a launch-angle and exit-velocity outcome, meaning a hitter's fly ball rate emerges naturally from their card's Launch Angle Distribution. High-FB power cards like Joey Gallo, Adam Duvall, and Kyle Schwarber boom-or-bust through the season — leading the sim in home runs while suppressing batting average. Pitching cards inherit their fly ball tendency from their pitch mix and zone profile, and matching a high-FB pitcher into a hitter-friendly park is one of the fastest ways to give up a five-run inning.