The Basketball Cube
At a friend's 27th birthday party — cube-themed, naturally — the conversation turned to a MrBeast video in which competitors ranging from age 1 to 100 faced off in athletic challenges1. In the final round, a 28-year-old played basketball free throws against a 7-year-old. The child couldn't physically heave the ball high enough to reach the hoop. It was, everyone agreed, spectacularly unfair. I pointed out that organized basketball already solves this problem: different levels of play use different hoop heights, ball sizes, and ball weights. Youth leagues don't ask 6-year-olds to shoot a full-size ball at a 10-foot rim any more than little league asks 8-year-olds to hit off a major league mound.
But I realized I wasn't totally sure about the details. Do women's professional leagues actually use a different ball than men's? Does the hoop height ever change, or just the ball? What about wheelchair basketball, deaf basketball, Special Olympics? The cube-themed party had planted the image in my head: three parameters, three axes, a cube of basketball configurations floating in space. So I asked Claude to look it all up.
| Category | Ball Size | Diameter | Weight | Hoop |
|---|---|---|---|---|
| Mini (Ages ≤4) | 3 | 7.0″ | 10 oz | 5.5 ft |
| Youth (Ages 5–6) | 4 | 8.1″ | 14 oz | 6.5 ft |
| Youth (Ages 7–8) | 5 | 8.75″ | 17 oz | 8.0 ft |
| Youth (Ages 9–11) | 6 | 9.1″ | 20 oz | 9.0 ft |
| Boys’ High School | 7 | 9.4″ | 22 oz | 10 ft |
| Girls’ High School | 6 | 9.1″ | 20 oz | 10 ft |
| NCAA Men’s | 7 | 9.47″ | 22 oz | 10 ft |
| NCAA Women’s | 6 | 9.15″ | 20 oz | 10 ft |
| NBA | 7 | 9.47″ | 22 oz | 10 ft |
| WNBA | 6 | 9.15″ | 20 oz | 10 ft |
| FIBA 3×3 | 6* | 9.15″ | 21 oz | 10 ft |
| Wheelchair (M) | 7 | 9.47″ | 22 oz | 10 ft |
| Wheelchair (W) | 6 | 9.15″ | 20 oz | 10 ft |
| Deaf (M) | 7 | 9.47″ | 22 oz | 10 ft |
| Deaf (W) | 6 | 9.15″ | 20 oz | 10 ft |
| Spec. Olympics (M) | 7 | 9.47″ | 22 oz | 10 ft |
| Spec. Olympics (Jr.) | 6 | 9.15″ | 20 oz | 8.0 ft |
*FIBA 3×3 uses a Size 6 circumference with Size 7 weight — the only hybrid ball in organized basketball2.
The ball is only part of the story. Three court parameters also vary across levels: court length, three-point line distance, and key (paint) width. Unlike the ball cube, these parameters don't collapse into two clusters — the NBA's court is longer than a high school's, its three-point line is four feet deeper, and its key is a third wider than what college players use. The WNBA sits between them: NBA-sized court and key, but FIBA's shorter three-point arc. Youth leagues below age 12 don't use a three-point line at all.
| Category | Court Length | 3-Point Line | Key Width |
|---|---|---|---|
| Junior High | 74 ft | 19′ 9″ | 12 ft |
| High School | 84 ft | 19′ 9″ | 12 ft |
| NCAA (M & W) | 94 ft | 20′ 9″ | 12 ft |
| WNBA | 94 ft | 22′ 2″ | 16 ft |
| NBA | 94 ft | 23′ 9″ | 16 ft |
| FIBA / WC / Deaf / SO | 92 ft | 22′ 2″ | 16 ft |
So back to the MrBeast video. That 7-year-old appears to be playing with a regulation NBA ball on a 10-foot hoop, and that's not what any basketball organization on earth would give a 7-year-old. USA Basketball guidelines call for a Size 5 ball (27.5-inch circumference, about 17 ounces) and an 8-foot hoop for that age. The challenge wasn't just unfair because of the age gap — it was unfair because the equipment was wrong. The 7-year-old was handed a ball 30% heavier than an age-appropriate ball and asked to throw it two feet higher than an age-appropriate regulation hoop3.
At the party I asked "where on the spectrum of basketball size between an 8 year old and adult men does every other demographic fit?", but I was simplifying too much - the better question was "what is the shape of the basketball parameter cube?"