The official size of a regulation men’s basketball (NBA and most men’s high school/college play) is 29.5 inches (about 75 cm) in circumference , with a diameter of about 9.4–9.5 inches (24–24.2 cm) and a weight up to about 22 ounces (620 g).

Quick Scoop

For context, different leagues use slightly different “official” sizes:

  • NBA / men’s high school & college (Size 7)
    • Circumference: about 29.5 inches (75 cm).
* Diameter: about 9.43–9.51 inches (24–24.2 cm).

* Weight: up to about 22 ounces (620 g).

* This is what most people mean by “official size of a basketball.”
  • WNBA / women’s high school & college (Size 6)
    • Circumference: about 28.5 inches (72–73 cm).
* Diameter: about 9.07–9.23 inches.

* Weight: about 18–20 ounces (510–550 g).
  • Official pressure range (pro ball)
    • Typically inflated to about 7.5–8.5 psi so it bounces correctly on hardwood courts.

Mini table of “official” game balls

[1][5][3] [1][3] [5][3] [7][3][5][1] [3][5][1] [7][5]
Level / League Size Circumference Diameter Weight
NBA (men) 7 ≈29.5 in / 75 cm ≈9.43–9.51 in Up to ≈22 oz / 620 g
WNBA (women) 6 ≈28.5 in / 72–73 cm ≈9.07–9.23 in ≈18–20 oz / 510–550 g

Little story to picture it

Imagine you walk into a gym where two games are about to tip off: on one court, an NBA-style men’s game; on the other, a top-level women’s game. The ball for the men’s game feels just a bit bulkier in your hands, stretching the fingers a little farther around its 29.5‑inch circumference. On the next court, the women’s ball looks nearly identical but turns out to be slightly smaller and lighter when you pick it up, making it a touch easier to grip and control for many players.

Quick TL;DR

  • Most commonly, “official size basketball” = Size 7, 29.5 in circumference (NBA, men’s high school and college).
  • Women’s official ball = Size 6, 28.5 in circumference (WNBA, women’s high school and college).

Information gathered from public forums or data available on the internet and portrayed here.