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What Is a Swing in Baseball?

This article will define one of the most controversial calls in baseball: a swing. Decisions on whether a complete swing happened have determined games, with the defense almost always arguing on the side of full swing, while batters arguing on the side of a checked swing. What is a swing in baseball?

A swing in baseball is when a batter fully commits to connecting with a pitch. Although there are no definitive rules to what a swing is, most people consider a swing to occur when a batter’s wrists roll over, when the bat clears home plate, or when the bat passes the front of the batter’s body.

A youth hitter is in the batter's box and in the middle of swinging at a pitch

Before you “balk” at reading this article, let me explain why players consider one of these three things to be a swing and how an umpire determines whether or not a batter attempted their swing.

When Does a Swing Become a Strike?

Believe it or not, the definition of a swing doesn’t exist in the MLB rule book. Players ask umpires to call a swing in almost every game, and such decisions can determine the outcome of an at-bat, but you won’t find the definition in any professional rule book.

After seeing multiple calls from umpires, baseball players have landed on three general ways to determine when a swing becomes a strike.

A swing becomes a strike when either of the following happens:

  • The batter’s wrists roll over.
  • The bat clears home plate.
  • The barrel passes the front of the batter’s body.

Most baseball fans use the above criteria to define when a swing becomes a strike. If the batter does either of the above and misses, it constitutes a strike. Let’s look at the above points in greater detail.

The Batter’s Wrists Roll Over

If you’re a batter, you’re allowed to swing at the ball or let it go by. Failure to hit a legal pitch results in a strike – three strikes and you’re out.

Checking your swing allows you to avoid a strike since a half swing isn’t considered a genuine offer for the ball. By failing to swing at a bad pitch, the pitch becomes a ball rather than a strike.

The term ‘breaking wrist’ stems from the motion of a batter trying to stop the bat’s movement towards the ball.

Proponents of this system argue when the batter’s wrists roll over, or the head of the bat crosses the wrists, the batter has swung. The batter successfully ‘halves’ a swing by keeping the wrists bent, and consequently, the bat away from the ball’s flight.

In 2014, Yasiel Puig of the LA Dodgers broke his bat while breaking his wrists to check a swing. Red Sox legend Jim Rice was allegedly also strong enough to snap his bat while trying to stop a full swing.

Breaking bats on check swings aren’t common, but a few professional players have been guilty of this feat. In fact, Carlos Santana, Willie Horton, and Reggie Sanders also did it.

The bats probably had cracks before the batters used them. However, it shows that it takes tremendous energy to halt the bat’s swing.

It’s interesting, however, that despite Puig’s efforts not to move his wrists, the umpire called a strike.

The Bat Clears Home Plate

This check leaves the batter and focuses on the distance the bat moves. For proponents of this system, it doesn’t matter whether the batter breaks their wrists or not.

The NCAA baseball rules state that a swing becomes a strike if the bat’s barrel passes home plate or crosses the batter’s front hip. However, the NCAA rules don’t apply to pro baseball. Furthermore, it’s difficult to determine whether a bat has cleared home plate, even when using cameras.

In pro baseball, a swing decision isn’t reviewable. The umpires decide in real-time whether to declare a swing a strike and sometimes they get help from another umpire who had a better angle.

Considering everything that the umpires have to monitor, it’s difficult for them to definitively say that a bat has cleared home plate. For instance, this clip shows an umpire deciding that a checked swing by a Giants’ batter isn’t a strike (most people believe it should have been a strike).

The decision saves the batter, who’s clearly relieved, and vexes the Dodgers, who feel ripped off by the umpire.

The umpires don’t have the benefit of a replay, but spectators do. And from the perspective of many fans, they believe the bat crossed home plate and should have been a strike.

To make it more complicated, different teams rely on different camera angles to support whatever decision favors them. In the video below, one camera angle can show that the bat crossed home plate, and another can show the batter stopped the bat before it crossed:

It’s a Strike When The Barrel Passes the Front of the Batter’s Body

This system also exists in the NCAA rules as an alternative to checking whether the bat clears home plate. The NCAA rules state that a swing becomes a strike if the bat passes the batter’s front hip.

A youth baseball player in a red uniform hitting a foul ball

It’s perhaps easier to check whether the bat has crossed the front hip than it is to check whether the bat has crossed home plate, making this test more reliable. Nonetheless, the call is still at the umpire’s judgment.

However, baseball is a fast sport, and it isn’t always clear whether the bat crossed the front hip. A batter looking to check a swing will retract the bat quickly, offering fans and umpires a few moments to see how far the bat traveled.

Every time a catcher catches a pitch on a check swing, the question, ‘did he go?’ rings around the stadium: nobody can be sure whether the batter swang, no matter how long they’ve watched baseball.

Baseball analysts can’t agree whether a batter has completed a swing or not based purely on the movement of their bodies. Even impartial watchers struggle to get the call right. This just goes to show how difficult it is to define what exactly a swing is in baseball.

What is a Checked Swing in Baseball?

Since there is no definitive definition of a swing in baseball, how do we know what a checked swing is? What constitutes a checked swing?

A checked swing, sometimes called a half swing, occurs when a batter begins their swing, but they do not fully commit to swinging at the pitch. In general, the bat does not travel far enough for an umpire to consider the attempt to be a swing.

Although there are no rules around what a swing is, there are rules in the MLB rule book on when a player can appeal a swing. When can you appeal a check swing?

Players can appeal a check swing when the pitch is ruled a ball and prior to the pitcher delivering the next pitch. Only the defense is allowed to appeal a check swing.

Once the defense appeals the check swing, the umpire must ask a base umpire for their judgment of the swing. Whatever the base umpire rules stands; no other appeals can be made.

How Do Umpires Decide When a Swing Becomes a Strike?

Ultimately, the umpires have to make a call: a safe gesture indicates a successful checked swing while a clenched fist indicates that the umpire considered the swing a strike. It’s sometimes a game-deciding call, sparking fury from the offensive team.

The home-base umpire decides whether they consider a swing a strike. If they call it a strike, their decision is final, as the rules don’t allow a batter to appeal the decision. If the umpire fails to call a strike, the catcher or pitcher can ask for an appeal, which the umpires consider.

Home base umpires rarely have the best view of the batter, so they often rely on the umpires at third and first base to decide.

Check swing appeals are provided for in the rule book (which is surprising as the rule book doesn’t define a swing). The rules provide that on appeal by the catcher or pitcher, the home plate umpire must consult the base umpire for their judgment on a half swing.

The umpire’s decision upon appeal is final. If the umpire calls a strike on a hitter facing his third strike, the batter has struck out.

Checked swings aren’t reviewable decisions: the umpires have no access to replays when deciding whether a batter swung. They rely on what they see, which sometimes produces wildly inconsistent decisions.

During the deciding playoff game between the LA Dodgers and the Giants in 2021, a controversial check-swing decision ended the contest in favor of the Dodgers.

Fans expressed their annoyance at the decision by tossing trash onto the Oracle Park turf.

Gabe Morales acknowledged that check swings are some of the most difficult decisions umpires make. The lack of camera replays makes the decision harder to call, but when he saw it live, he thought Flores swung.

Morales said that he’d watched a replay of the game-deciding pitch but declined to answer when asked whether he stood by his choice.

Ultimately, the call on whether a swing translates to a strike lies with the umpire and their interpretation of a swing. There’s no push to make the check swing a reviewable decision, so for now and into the foreseeable future, umpires have the final say on swings.

Can We Use Technology To Decide When a Swing Becomes a Strike?

The biggest issue with a swing is that we don’t have a rule that defines it. The definition swings (pun intended) from game to game, from umpire to umpire. So what is the solution?

We can use technology to decide when a swing becomes a strike if the MLB approves its use. In particular, an advanced form of the technology the MLB uses to track pitches can also help to refine swing and strike decisions.

The Giant’s heartbreaking end to what could have been one of the greatest baseball seasons reignited talks of introducing technology to assist umpires in making check-swing decisions. Most pitches have Hawk-Eye cameras, which could have helped Gabe Morales make a more informed decision during that crucial 2021 playoff game.

Following that debacle, Hawk-Eye revealed that it has been working on bat-tracking. Justin Goltz, the commercial director of Hawk-Eye Innovations, stated that the company is trying to decrease processing time so umpires can receive bat data in real-time.

However, before the MLB considers introducing technology, it needs to define a swing. It’s impossible to regulate something that is undefined; inaction from the MLB has forced the baseball community to define rules that umpires don’t apply across the board.

For instance, a potential rule can define a swing by the distance of bat movement. If the bat crosses a certain point – like the home plate’s tip – umpires could consider it a swing.

A rule around what is a swing could bring consistency and allow the implementation of technology in deciding when a swing becomes a strike.

Some baseball fans wonder why there’s such a big fuss about swings in baseball. They opine that the inconsistency of swings should remain because it adds spice to the game.

Yankees fan Zachary Morgenstern, an author for Fansided, is one such fan.

In July 2021, he penned an article about check swings after Rafael Devers of the Boston Red Sox was called out on strikes during a game against the Yankees. Rafael seemed to check his swing on the last strike, but the umpires disagreed.

Morgenstern opined that as a Yankees fan, he was delighted at Devers’ strikeout. However, he was more delighted that an umpire’s decision robbed his team’s bitter rivals.


A swing in baseball depends on the intention of the batter and the interpretation of the umpire. No one can authoritatively tell you when a swing becomes a strike, but to eliminate inconsistency as much as possible, the batter’s intention should be our guide.

The physical ways concocted to monitor when a swing becomes a strike are too ambiguous. They were created by studying umpires and the criteria they (maybe) use when determining a full swing.

At the moment, we rely on the umpires to decide depending on their observations. The batter is perhaps the most disadvantaged as they can’t appeal an umpire’s decision.

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Steve Nelson

I'm the owner of Baseball Training World. I live in Denver, Colorado and I enjoy playing baseball in an adult baseball team in the surrounding area. Read more about Steve Nelson.

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