What are GB%, LD%, FB%, and IFFB%?

GB%, LD%, FB%, and IFFB% Definitions

GB%, LD%, FB%, and IFFB% stand for the following –

  • Ground ball percentage
  • Line drive percentage
  • Fly ball percentage
  • Infield fly ball percentage

These are important statistics which can be tracked for both pitchers and hitters. The percentage of balls in play that a player has in each of these four categories helps to determine that player’s strengths and weaknesses. 

If you’ve ever heard the term ‘fly ball pitcher’ or ‘ground ball pitcher’, those classifications can be easily determined by using these stats. 

The Concept of GB%, LD%, FB%, and IFFB%

When evaluating a player, it is helpful to know what kind of “ball in play events” that player is most likely to create, because they are not all of equal value.

Naturally, line drives are good news for hitters and bad news for pitchers, as that type of ball in play turns into a hit at a high rate. On the other side of the coin, infield flies are great for pitchers and terrible for hitters, as they almost never fall in. Ground balls turn into hits fairly often when they get through the infield, but they rarely become extra base hits (and never home runs, obviously). With fly balls, the rate of hits is going to be rather low, as many of them are caught, but hitting a lot of fly balls can mean the player will end up hitting a significant number of home runs. 

Reviewing these four stats for a given player is a great way to bring their statistical performance ‘to life.’ Seeing that a batter is hitting .300, or that a pitcher has a 2.00 ERA is a starting point, but it doesn’t say anything about how the player reached those numbers. These categories help you gain a better understanding of performance even if you’ve never actually seen a given player on the field. 

Why are GB%, LD%, FB%, and IFFB% Important?

Using these four stats is important because it provides insight into player performance, helping to explain why a particular player is faring well, or why he might be struggling. It alsohelps to identify environments where one player might be a better fit over another. 

For instance, bringing in a fly ball pitcher to a stadium known for giving up a high rate of home runs would be a recipe for disaster. On the other hand, bringing a hitter known for a high FB% into that same environment could be a perfect fit. 

How are GB%, LD%, FB%, and IFFB% Calculated?

Fortunately, the calculations here are extremely simple and they’re basically the same, but we’ve listed them all out for your convenience. 

  • GB% = Ground Balls / Balls in Play
  • LD% = Line Drives / Balls in Play
  • FB% = Fly Balls / Balls in Play
  • IFFB% = Infield Fly Balls / Fly Balls

Note that the first three statistics are divided by balls in play, while IFFB% is divided only by the number of fly balls specifically. 

Each time the ball is put in play, a statistics service such as Baseball Info Solutions places that event in one of these four categories. As the games go by and players rack up balls in play and patterns will start to develop. You can easily calculate these rates yourself using the raw numbers, or you can just look up ball in play percentages at FanGraphs

What is a Good GB%, LD%, FB%, and IFFB%?

These aren’t statistics where we can easily identify what is good or bad in terms of performance. Each player is unique, and the optimal mix of ball in play types will vary dramatically from one player to the next. 

To highlight these differences, let’s look at the ball in play mix for two very different players. 

During the 2018 season, both Dee Gordon and Nelson Cruz played for the Seattle Mariners. They had the same home ballpark for the season, of course, making these comparisons particularly relevant. Let’s take a look at their respective rates for the 2018 season: 

Stat Dee Gordon Nelson Cruz
GB% 55.2% 44.0%
LD% 22.4% 17.5%
FB% 22.4% 38.5%
IFFB% 4.9% 11.0%

The differences are obvious. Dee Gordon, as one of the fastest players in baseball, wants to keep the ball on the ground and use his speed to his advantage. Without much power, most of the fly balls he hits are going to turn into outs, so the goal is to avoid hitting the ball high in the air. As a result, more than three-quarters of the balls put in play by Dee Gordon in 2018 were either line drives or ground balls. 

Nelson Cruz has a different plan. Where Dee Gordon brings speed to the table as his elite skill, Nelson Cruz offers his team raw power. He can hit the ball as hard as nearly anyone in the league, so elevating the ball is going to lead to home runs. And, without the speed that Gordon carries, ground balls are usually going to be outs. In the end, he managed a fly ball rate of 38.5%, which helped him rack up 37 home runs on the season. 

What are the Problems with GB%, LD%, FB%, and IFFB%?

Sample size is a notable problem with these four stats, as you need a large sample of balls in play to draw meaningful conclusions. 

For instance, if you were to look at the results of just three or four starts for a given pitcher, you wouldn’t be able to rely on the data as being indicative of true talent. For pitchers, you will want to view at least a full season worth of data, if not more. While the rates might stabilize a bit sooner for hitters, you still want to use as much data as possible to develop an accurate picture of hitting ability.