# Ball diameters by sport, derived from governing-body specifications — version 1.0, last checked 2026-08-14. License CC BY 4.0. Every figure is quoted from the source in its row.
Ball,Official circumference,Diameter (derived),Min. clear opening,Official weight,Specification source,Source URL,Source checked
"Basketball, size 7 (men's / adult)",29½–30 in,9.4–9.5 in,9.75,— (not stated in the cited source),NCAA men's basketball rules,http://fs.ncaa.org/Docs/stats/m_basketball_RB/2018/Rules.pdf,2026-08-14
"Soccer ball, size 5 (adult)",68–70 cm (27–28 in),8.5–8.8 in,9,410–450 g (14–16 oz) at the start of the match,"IFAB Laws of the Game, Law 2",https://www.theifab.com/laws/latest/the-ball/,2026-08-14
"Volleyball, indoor",65–67 cm (25.6–26.4 in),8.1–8.4 in,8.5,260–280 g (9–10 oz),"USA Volleyball Indoor Rules 2025-2027, Rule 3.1",https://usavolleyball.org/wp-content/uploads/2023/03/2025-2027-USAV-Indoor-Rules-Book_FINAL.pdf,2026-08-14
"American football, official size",21–21¼ in around the middle; 28–28½ in end to end,6.7–6.8 in,7,14–15 oz,"Official Playing Rules of the NFL, Rule 2",https://operations.nfl.com/rules-officiating/2026-nfl-rulebook,2026-08-14