What is the Diameter of a Regulation Baseball?

- September 5, 2023

A regulation-size baseball measures approximately 2.86 to 2.94 inches (7.3 to 7.5 centimeters) in diameter. Its circumference is between 9 and 9.25 inches (22.9 to 23.5 centimeters). 

As for the weight of baseballs, they range from 5 to 5.25 ounces (142 to 149 grams). 

Evolution of the Baseball

Evolution of the baseball

Prior to 1876, there was no standardization with regards to the size of the baseball. The National League first regulated the size, and in 1911, a newly designed ball made with a cork-core came into play. For the rest of the decade, the National League used this ball because it traveled farther than the old balls that had a rubber core. 

Babe Ruth emerged as a power hitter around the time that the baseball allegedly changed in 1920. Although there was no evidence of the new ball allowing players to hit the ball with greater speed and distance, offensive statistics rose. This could have also been because Ruth showed that power was a legitimate part of the game, and players strived more for the home run than ever before. 

In any event, the new baseball was said to be constructed using a more premium-grade Australian yarn.

A standard for the baseball was put into place for all of Major League Baseball in 1934. The official regulation ball was constructed with a cork center, two yarn wrappings, a rubber cement coat, two more yarn wrappings, and a horsehide cover. Changes were made later to a cowhide leather exterior.

In 1975, MLB ended its relationship with Spalding. In 1976 Rawlings became the official supplier of balls for MLB, which are still used today.

Famous Baseballs in History

Arguably, the most famous of Babe Ruth’s homes runs was his “called shot” in Game 3 of the 1932 World Series. However, one of the most famous baseballs in history is one in existence that is worth over $800,000 and was signed by Ruth on a home run ball hit in 1933.

The 756th home run by Barry Bonds to set the all-time record for most home runs in a career was auctioned for nearly $750,000.

Although not a home run ball, the ball hit between Bill Buckner’s legs in the 1986 World Series to lead the Mets to a win sold for over $418,000.

Notable home runs in baseball history include the following

  1. Babe Ruth’s “called shot” in the 1932 World Series
  2. Bobby Thompson’s walk-off home run to win the 1951 World Series
  3. Bill Mazeroski’s walk-off home run in Game 7 of the 1960 World Series
  4. Hank Aaron’s 714th home run to break Babe Ruth’s record in 1974
  5. Carlton Fisk’s game-winning home run in Game 6 of the 1975 World Series
  6. Bucky Dent’s home run to defeat the Red Sox in game 163 of the 1978 seasons. This sent the Yankees to the playoffs.
  7. Kirk Gibson’s pinch-hit home run against Dennis Eckersley in the 9th inning after hobbling to the plate to win game one of the 1988 World Series.
  8. Joe Carter’s walk-off home run in 1993 to win the World Series.

Differences in Baseballs

The “ordinary baseball” is the standard baseball used for MLB games, which Rawlings makes. In Japan, the “ordinary baseball” is also used in high school games and is generally referred to as a “hard ball.”

The rubber baseball is used in a Japanese-style game and consists of two types. The first is the major ball that measures 2.81 to 2.85 inches (7.15 to 7.25 centimeters) in diameter. The second type, a junior version, measures 2.7 inches to 2.74 inches (6.85 to 6.95 centimeters) in diameter.

The soft baseball, which is a compression ball, is made from a polyurethane material. The softness varies but is rated by levels. Generally, these balls are bigger and heavier than ordinary baseballs. Not used in gameplay, these balls are used basically for fielding or batting practice

T Balls

Similar to baseball, T-ball is played by children ages 4-8. The most significant difference in the game is that there is no pitching at this level. Players hit the ball off a stationary tee. T-ball USA dictates all rules and regulations of the game. The ball used in T-ball is smaller and lighter than a regular baseball. 

You can find this ball in any sporting goods store. Simply look for a ball that is marked for T-ball. Those that are marked as an “official T-ball” are official balls that can be used in leagues. 

The circumference of the ball should be between 9 and 9.5 inches, and the ball will weigh in between 4 and 5 ounces. In addition, a T-ball is much softer than a regulation baseball. The center of the ball is sponge rubber or a molded core.

Other Specifications

Even if a ball’s dimensions are correct, it doesn’t meet specifications unless it is the proper shape and constructed of the appropriate materials. A ball must be spherical in shape, with a core made of cork or other similar materials. The core must be wrapped in yarn and covered with either two strips of cowhide or two strips of horsehide.

With an average baseball remaining in play in a Major League game for five to seven pitches, there are over 600,000 balls used throughout the season. 

Quality Control

A representative sample of each shipment of baseballs is tested to measure the resiliency of a baseball. 

The test, known as CORE, involved shooting a baseball from a cannon at 85 feet per second at a wooden wall from eight feet. The speed at which the ball rebounds from the wall is then measured. A ball that rebounds between 51.4 and 57.8 percent of the initial velocity meets MLB specifications.

Not only must a baseball meet velocity requirements, but it must also keep its shape after being hit 200 times with a force of 65 pounds. The distortion must be less than .08 inches after being compressed.

Baseballs in the Future

There’s very little indication that the size, construction, and materials used will change in the near future. Perhaps manufacturers will use a more efficient process to make the baseballs. After all, with increased technology, manufacturers could use automated machines to speed the process. Some problems must be resolved, such as beginning and ending the stitching process without manual assistance. 

One issue that may never go away is the suspicion that baseballs are “juiced”. This causes them to be harder and travel farther. 

This will vary from year to year as the number of home runs in the league fluctuates.

How Much Does an MLB Baseball Cost?

The cost comes in at about $7 per ball. The league will buy about one million baseballs every season. If you factor in the cost of shipping, MLB will put out upwards of $10 million just on baseballs to use for an entire season.

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