How Big Is a Basketball? Official Sizes & Dimensions

By Emma Wilson · July 15, 2028

A standard basketball used in professional men's games, such as the NBA, has a circumference of 29.5 inches (74.9 cm) and a diameter of approximately 9.4 inches (23.9 cm). This size is classified as Size 7 and is designed for players aged 12 and up.

Understanding Basketball Sizes

Basketballs come in various sizes depending on the league, gender, and age group. The size affects grip, control, and overall performance on the court. Below is a breakdown of common basketball categories.

Standard Basketball Size by League and Age

Size 7 (29.5 inches): Used in NBA and official men's competitions (ages 12+)
Size 6 (28.5 inches): WNBA and youth players ages 12-14
Size 5 (27.5 inches): Ideal for children ages 9-11
Size 4 (25.5 inches): Designed for kids under 8 years old
Mini (16-20 inches): Promotional or recreational use, not for gameplay

Diameter and Circumference Explained

While circumference is the most commonly cited measurement, diameter gives a clearer idea of how large the ball appears when held or bounced. The formula to convert circumference to diameter is diameter = circumference ÷ π.

Basketball Size	Circumference (inches)	Circumference (cm)	Diameter (inches)	Diameter (cm)	Weight (oz)	Weight (g)
Size 7 (Men)	29.5	74.9	9.4	23.9	22	624
Size 6 (Women)	28.5	72.4	9.1	23.1	20	567
Size 5 (Youth)	27.5	69.9	8.8	22.4	17	482
Size 4 (Mini Kids)	25.5	64.8	8.1	20.6	14	397
Mini Ball	16–20	40.6–50.8	5.1–6.4	13.0–16.3	8–12	227–340

Table data source:1, 2

The data shows that adult men's basketballs are not only larger in circumference but also heavier, which impacts shooting mechanics and dribbling speed. Women's and youth balls are scaled down to accommodate smaller hand spans and developing strength. The consistent proportionality across sizes ensures skill transfer as players grow.

Material and Inflation Standards

Besides size, material and air pressure influence how a basketball feels and performs. Most official balls are made from composite leather, rubber, or genuine leather.

Key Factors Affecting Ball Performance

Air Pressure: Recommended at 7.5–8.5 psi for optimal bounce
Surface Type: Leather for indoor courts; rubber for outdoor durability
Grip Texture: Peppercorn or tumbled finish enhances control
Bladder Quality: Latex or butyl bladder affects air retention and responsiveness

Frequently Asked Questions About Basketball Size

How big is a regulation basketball in the NBA?

A regulation NBA basketball is Size 7 with a circumference of 29.5 inches (74.9 cm) and a diameter of about 9.4 inches (23.9 cm).

What is the difference between men's and women's basketball size?

Men's basketballs (Size 7) have a 29.5-inch circumference, while women's (Size 6) are 28.5 inches. The smaller size improves handling for average hand size in female players.