# Can I dunk a basketball?

Computes the vertical jump you need to dunk a basketball from your standing reach, the rim height and how far above the rim your hand must reach, and says whether your vertical jump is enough.

- Page: https://www.acalculator.org/sports/dunk-calculator
- JSON spec: https://www.acalculator.org/sports/dunk-calculator.json
- Version: 374b55ebf096

## Default answer

Example with the default inputs (Standing reach 96 in, Your vertical jump 26 in, Rim height 120 in, Reach above the rim 6 in): With a standing reach of 96 in, you need a vertical jump of 30 in (76.2 cm) to dunk on a 120 in rim.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| reach | Standing reach | How high you can touch standing flat-footed with one arm stretched straight up. |
| jump | Your vertical jump | How much higher you can touch at the top of a jump than your standing reach. |
| rim | Rim height | The height of the top of the rim above the floor: 10 ft on a regulation hoop. |
| over | Reach above the rim | How far above the rim your hand must reach to put the ball down through it. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| needed | Vertical jump needed (in) | Rim height + reach above the rim − standing reach, in inches, or 0 if you reach that high standing. |
| neededCm | Vertical jump needed (cm) | The vertical jump needed, in centimetres. |
| dunk | Can you dunk? | Yes when your vertical jump is at least the vertical jump needed. |
| margin | Your jump minus the jump needed | Your vertical jump − the vertical jump needed, in inches; below 0, how much more you need to jump. |
| marginCm | Your jump minus the jump needed (cm) | The same difference, in centimetres. |
| top | Your reach at the top of the jump | Standing reach + your vertical jump, in inches. |
| topCm | Your reach at the top of the jump (cm) | The same reach, in centimetres. |
| speed | Take-off speed needed | The upward speed at take-off that reaches the vertical jump needed: √(2 × g × jump needed). |
| hang | Hang time of that jump | Time in the air for the vertical jump needed, up and down: 2 × √(2 × jump needed ÷ g). |

## Method

vertical jump needed = rim height + reach above the rim − standing reach (0 if negative); take-off speed = √(2 × g × jump); hang time = 2 × √(2 × jump ÷ g), g = 9.80665 m/s².

## Assumptions

- The reach above the rim is how high over the rim your fingertips must get to push the ball down through it. 6 inches is a common rule of thumb for a one-hand dunk; people with small hands, or who dunk with two hands, need more. Change it to suit you.
- Standing reach and vertical jump are measured as on a vertical jump test: flat-footed reach with one arm, then the extra height touched at the top of a jump.
- Take-off speed and hang time use projectile motion with no air resistance and standard gravity, g = 9.80665 m/s².
- Lengths are added and subtracted exactly as typed; values are rounded only for display.

## Worked examples

1. reach = 2.4384, jump = 0.6604, rim = 3.048, over = 0.1524 gives needed = 30, neededCm = 76.2, dunk = no, margin = -4, marginCm = -10.16, top = 122, topCm = 309.88, speed = 3.86592, hang = 0.788428. Source: NBA Official Rule No. 1, Section II (the rim is 10 feet above the floor), https://official.nba.com/rule-no-1-court-dimensions-equipment/.
2. reach = 2.286, rim = 3.048, over = 0.1524 gives needed = 36, neededCm = 91.44. Source: 120 + 6 − 90 = 36 in (rim height from NBA Official Rule No. 1, https://official.nba.com/rule-no-1-court-dimensions-equipment/).
3. reach = 2.7, jump = 0.6, rim = 3.05, over = 0.15 gives needed = 19.685039, neededCm = 50, dunk = yes, margin = 3.937008, marginCm = 10, topCm = 330, speed = 3.131557, hang = 0.63866. Source: FIBA Official Basketball Rules 2024, Basketball Equipment (the ring is 3,050 mm above the floor).
4. reach = 2.5, jump = 0, rim = 2.1336, over = 0.1524 gives needed = 0, neededCm = 0, dunk = yes, margin = 0, speed = 0, hang = 0.

## FAQ

### How high do I need to jump to dunk?

Take the rim height, add how far above the rim your hand must reach, and subtract your standing reach. With a standing reach of 8 feet (96 inches), a 10-foot rim (120 inches) and 6 inches above the rim: 120 + 6 − 96 = 30 inches of vertical jump.

### How do I measure my standing reach?

Stand flat-footed next to a wall, stretch one arm straight up and mark the highest point your fingertips touch. The height of that mark is your standing reach. Measure it rather than guess from your height: arm length varies a lot between people of the same height.

### How do I measure my vertical jump?

Jump from a standstill next to the same wall and touch as high as you can. Your vertical jump is the height of that touch minus your standing reach. Take the best of three tries.

### How far above the rim do I need to reach to dunk?

The calculator uses 6 inches as a starting point. You need enough height to hold the ball above the rim and push it down through, so people with small hands, or who dunk with two hands, need more. Change Reach above the rim to suit you.

### How high is a basketball rim?

A regulation rim is 10 feet (3.05 m) above the floor in the NBA, college, high school and FIBA play. Youth hoops are often lower, for example 8 or 9 feet; enter the height of the hoop you play on.

### What do take-off speed and hang time mean?

They describe the jump you need. Take-off speed is how fast you must leave the floor to rise that high, √(2 × g × height). Hang time is how long that jump keeps you in the air, up and down, 2 × √(2 × height ÷ g). A 30-inch jump needs about 8.65 mph at take-off and lasts about 0.79 seconds.

## Sources

- NBA Official Rules, Rule No. 1, Section II, Equipment (the upper edge of the basket ring is 10 feet above the floor). https://official.nba.com/rule-no-1-court-dimensions-equipment/
- FIBA Official Basketball Rules, Basketball Equipment (the upper edge of the ring is 3,050 mm above the floor). https://www.fiba.basketball/documents
- NIST, standard acceleration of gravity, g = 9.80665 m/s² (exact). https://physics.nist.gov/cgi-bin/cuu/Value?gn
- OpenStax, College Physics 2e, §2.7 Falling Objects (v² = 2gh for a vertical launch). https://openstax.org/books/college-physics-2e/pages/2-7-falling-objects