What Are the Different Softball Sizes? Don’t Worry, I’ll Explain.

Call me old school, but I keep my teams’ balls in buckets. And, occasionally, one of my softball players will reach in grab a ball, not realizing it’s too big (I coach 10U) until I say something. It doesn’t happen often, but it happens enough that a post highlighting the different softball sizes is probably necessary. 

The reality is there are a couple of different softball sizes, and the sizes depend on the player’s age, the league’s rules, and whether it’s fastpitch softball or slow pitch softball. Whether you’re a parent wondering which ball size to buy so your player can practice at home, or a player wondering when the ball is going to get bigger, I’ll explain common sizes used in fast pitch softball, slow pitch softball, and everything between age 8 and 18U.

How Are Softballs Measured?

Before I go too deeply into the different softball sizes, let’s mention how softballs are mentioned. 

When we refer to a softball’s size, we’re describing the circumference of the ball, or the measurement around the middle of the ball. If you were to take a string, wrap it around the middle of the ball, mark it, and then lay it out on a tape measure or ruler, you’d get the size of the ball.

But if you need to know the diameter of a softball, 11-inch softballs are 3.5 inches across, and 12-inch softballs are about 3.8 inches across.  

Softball Sizes by Age Group and League

Softballs come in three primary sizes: 11-inch, 12-inch, and occasionally 10-inch. These sizes correlate closely with the age group and the league you’re playing in, whether it’s Little League, Cal Ripken/Babe Ruth, or other leagues.

8U Softball Size

For the youngest youth softball players, usually ages 6 to 8, the 8 softball size refers to a smaller, often 10-inch ball. These are easier to throw, catch, and hit, helping kids build confidence and improve coordination. These are used in slow pitch softball and fastpitch softball.

• Found in the youngest divisions or instructional divisions
• Easier grip for small hands
• Ideal for practice and entry-level softball games

But, this comes with a disclaimer: I have never personally seen 10-inch softballs in all my years of coaching. However, it appears they do exist in some leagues and areas. My 6U rec and 8U travel teams have always used the 11-inch ball.

10u Softball Size

In 10u (10 and under) divisions, most leagues begin transitioning to 11-inch softballs. This is the most widely accepted size for fastpitch games in this age group.

• Helps bridge the gap between coach pitch and full-speed pitching, such as in fast pitch softball.
• Used in many fast pitch softball tournaments and leagues

Again, my players started using an 11-inch ball at 6U rec and continued to use the same size ball through 10U. 

12U Softball Size

By 12U, players graduate to the 12-inch ball—the same size used in high school, college, and adult fastpitch competition. They’re basically playing by the same exact rules at this point, so it’s time to use the bigger ball. 

• The 12-inch ball becomes the standard
• Players face increased pitching distance and speed
• Encourages stronger throws and quicker bat speed

This can be a tough transition because smaller players may not be able to fully grip the ball yet. And the increased pitching distance (40-feet as opposed to 35) and wind-resistance can make throwing strikes difficult, and it’s typically the taller, stronger girls who can pitch at this level. 

14U Softball Size

The 14U softball size remains 12 inches, as the focus shifts to refining skills like reading line drives, proper swing mechanics, and quicker pitch recognition during softball games.

• Used in more advanced fast pitch softball leagues
• Umpires and coaches start enforcing ASA rules more strictly
• Players prepare for varsity and travel ball levels

Again, the softball size doesn’t change here, but most players can get a good grip on the ball. Pitching distance does move back to standard regulation here (43 feet), and this is often where many youth pitchers move to other positions. 

16U Softball Size

At 16U, the 12-inch ball is used exclusively. Athletes now train for elite travel teams and showcase tournaments.

• Softball players prefer game-ready 12-inch balls for consistent performance
• Fields and pitcher’s plate distances match high-level fastpitch standards
• Emphasis on reaction time and advanced defense

This is the real game at full-speed. 

18u Softball Size

In 18U, the 12-inch softball is used again, just like in professional, college softball, and Olympic competition softball games.

• The game is played at full regulation size
• Expect top-level pitch speed, strategy, and competition
• Coaches focus on preparing athletes for college recruitment

Slowpitch Softball Size

Slow pitch softball uses a 12-inch ball in most co-ed, recreational, and adult leagues. However, some slow pitch leagues for women or beginners may use an 11-inch ball for a better grip. In my opinion, that’s completely unnecessary, but those are the rules. 

• Slower pitch speeds mean the larger ball doesn’t lose velocity mid-air in slow pitch softball games.
• Defense needs to react quickly on line drives of the softball
• Nine players typically play defense, with emphasis on batting order, strategy, and precision hit placement during slow pitch softball games.

If you’re gearing up for a slow pitch softball game, check the league rules to confirm your softball size—some slow pitch softball rules vary by gender or age group.

Why Softball Sizes Matter in the Sport

The size of the ball affects bat performance, throwing mechanics, and player safety while playing softball. As pitching distance and speed increase, so does the need for standardized equipment. Using the correct ball size helps maintain fairness, improves play, and keeps the game competitive.

Plus, using the wrong size ball could result in rule violations or player injury. I wouldn’t want a strong 18U batter driving an 11-inch ball back at a pitcher or infielder. You could make the argument that 18U baseball players hit a 9-inch ball back at the defense, but softball fields are 33% smaller, meaning fielders are much closer to the batter. 

Final Thoughts

From 8U to 18U, and from fastpitch to slow pitch, understanding softball sizes is crucial for safe and effective play. Whether you’re a coach, player, or parent, make sure you’re using the correct size for your league, age group, and play style.

Still unsure which ball to use? Reach out to your league director or check the official ASA rules for clarity.