The diameter of a basketball rim is 18 inches. The rim top is 120 inches (10 feet) off the ground surface. While the rim size is virtually universal, there are variations in the dimensions of the basketball court.
The length is 94 ft / 28.65 m. The court is 50 ft / 15.24 m wide and the center circle is 12 ft / 3.66 m in diameter. The three point distance is 23.75 feet or 7.2 m. From the sides it is 22 ft (6.7 m). The shaded lane or key is 16 ft (4.8 m) wide. The free throw distance is 15 ft.
Basketball Courts in Detail
Aside from knowing the diameter of a basketball rim, you will also become more adept if you are familiar with the other sections of the court. The center circle is where the tipoff takes place. Before the tipoff, only the two players jumping in the center can step in the center circle. Usually these players are the centers of the teams.
The three point line marks the point that separates the three point area from the two point section. Any shot made at the three point area will count for three points. As indicated above, the 3 point distance in the NBA is 23.75 ft (22 ft at the sides).
In FIBA basketball it is 22.15 ft. In NCAA men’s basketball it is 20.75 feet (6.32 m). For NCAA high school women’s it is 19.75 feet (6.02 m). At the WNBA it is 20.5 feet (6.2 m). Note: if a player steps on the three point line and makes the shot, it will only be two points.
About the Perimeter
These are the sections that are the farthest from the rim. The perimeter is within the three point line but outside the foul throw section. Shots attempted in this area are called jump shots, medium range shots or perimeter shots.
The Low Post Area and the Key
The low post area is the section that is nearest the rim but not inside the foul throw region. This is one of the most frequent scoring areas in the game. The key is the painted part under the rim. It is 12 feet (3.7 m) wide in the NCAA. In the NBA it is 16 feet (4.9 m) wide.
The diameter of a basketball rim has remained constant through the years. Unlike the other parts of the court, its specifications have not changed.