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How Your Dunk Height Is Calculated
To dunk, your hand has to get above the rim in a jump, with enough room to bring the ball over it. The highest point you can touch is your standing reach plus your vertical jump. This calculator compares that point with the rim and with a dunk target a few inches higher.
What Your Max Reach Measures
Your max reach is the height of your fingertips at the top of your jump. It depends on your flat-footed standing reach (your height plus your arm length) and how high you jump. This is how the NBA Draft Combine defines a vertical jump: the highest point touched minus standing reach³. Max reach does not measure ball control or timing, which you also need to dunk.
The Formula
Max reach = standing reach + vertical jump
Rim gap = max reach - rim height
Dunk target = rim height + clearance (6 in if you can palm the ball, 8 in if you can't)
Dunk gap = max reach - dunk target
Vertical needed to dunk = dunk target - standing reach
The rim is 10 ft (120 in) above the floor in NBA rules¹ and 3,050 mm (3.05 m) in FIBA rules².
How This Calculator Computes Your Result
Enter your standing reach and your vertical jump in feet and inches or centimeters, say whether you can palm a basketball, and choose a rim height (10 ft regulation is the default). If you don't know your reach, the tool can estimate it as your height without shoes x 1.33. That ratio comes from NBA Draft Combine players, whose average standing reach was 1.330 to 1.338 times their height across all positions³.
The result shows your max reach, how far it is above or below the rim and the dunk target, and the vertical you would need to touch the rim and to dunk. Lengths are rounded to 0.1 in or 0.1 cm. In metric mode the regulation rim is 305 cm.
What Your Result Means
Result | What it means |
Dunk range | Your max reach is at or above the dunk target |
Rim range | You can touch the rim but are short of the dunk target |
Below the rim | Your max reach is lower than the rim |
The dunk target adds room for the ball. To dunk, the ball must get over the front of the rim and down through the ring. A size 7 ball is 750 to 770 mm around², so it is about 9.4 to 9.6 in across. The ring is 18 in wide on the inside¹.
The 6 inch and 8 inch clearances are common rules of thumb, not measured values. Palming lets you control the ball with one hand at full reach. If you can't palm, you have to cradle the ball against your wrist or use two hands, so dunk tools commonly allow more height.
How to Measure Correctly
Standing reach: stand flat-footed, side-on to a wall. Reach straight up with the arm nearest the wall and mark your fingertips. Wear the shoes you will jump in.
Vertical jump: jump and touch the wall as high as you can, then subtract your standing reach. Use the same approach you would use to dunk, such as a one-step or a short run-up.
Do three to five jumps with rest between them and use your best.
Don't use a jump mat or app number here. They time how long you are in the air, so they miss your arm reach. A 2019 review noted that reach devices need the arms and did not recommend them for measuring jump height⁵. For dunking, though, arm reach is exactly what counts.
How NBA Prospects Compare
At the NBA Draft Combine (3,610 players, 2000 to 2018), the max vertical is a running jump measured as jump reach minus standing reach³. Using the drafted players' average values, every position cleared a 3.05 m rim comfortably:
Position | Standing reach | Running vertical | Max reach above rim |
Point guard | 8 ft 1.6 in (247.8 cm) | 36.2 in (91.9 cm) | 13.7 in (34.7 cm) |
Shooting guard | 8 ft 4.9 in (256.4 cm) | 35.7 in (90.8 cm) | 16.6 in (42.2 cm) |
Small forward | 8 ft 8.0 in (264.1 cm) | 34.9 in (88.6 cm) | 18.8 in (47.7 cm) |
Power forward | 8 ft 11.1 in (272.0 cm) | 33.7 in (85.5 cm) | 20.7 in (52.5 cm) |
Center | 9 ft 1.5 in (278.2 cm) | 31.9 in (81.1 cm) | 21.4 in (54.3 cm) |
Taller players jumped less on average but still reached higher. From point guard to center, standing reach rose by about 30 cm while the running vertical fell by about 11 cm. Jump height also stood out among the best dunkers. In the NBA Slam Dunk Contest, finalists were shorter (193.4 vs 200.1 cm) and had less standing reach (257.7 vs 268.3 cm) than players knocked out early, but they jumped higher (102.4 vs 94.8 cm)⁴.
Standing Jump vs Running Jump
If you dunk off a run-up, measure that jump. At the combine, running jumps averaged about 10 to 15 cm (4 to 6 in) higher than no-step jumps in every position group³. Arm swing also matters: it can change jump performance by about 8 to 11%⁵.
NBA Combine Running Vertical and Reach Above the Rim
Averages for drafted players by position. Taller positions jumped less but still reached higher.
- Running vertical
- Max reach above the rim
Show data table
| Position | Running vertical (in) | Max reach above the rim (in) |
|---|---|---|
| Point guard | 36.2 | 13.7 |
| Shooting guard | 35.7 | 16.6 |
| Small forward | 34.9 | 18.8 |
| Power forward | 33.7 | 20.7 |
| Center | 31.9 | 21.4 |
A Note on Accuracy
Your result is only as good as your two numbers. Every inch of error in your standing reach or jump shows up as an inch in the result. The estimate from height uses NBA players, whose wingspans were about 5 to 7% longer than their height³, so it may run high for most people. Measure your reach if you can. The clearance is a rule of thumb, and your own hand size and ball control will move it up or down.
Frequently Asked Questions
How high do you have to jump to dunk?
Take the rim height (120 in), add about 6 inches of clearance, and subtract your standing reach. With an 8 ft (96 in) standing reach and the ability to palm the ball, that is about a 30 inch vertical.
How tall do you have to be to dunk?
There is no minimum height, because your jump can make up for a shorter reach. Using the height estimate, a 6 ft person who can palm the ball needs about a 30 inch vertical, or about 32 inches if they can't.
What is a good vertical jump for dunking?
A good vertical for dunking is one that lifts your max reach at least about 6 inches above the rim. Drafted NBA guards averaged a running vertical of about 36 inches at the combine³.
How accurate is a dunk calculator?
It is as accurate as your measurements and the clearance estimate. A measured standing reach and a wall-test vertical give a much better answer than a height-based estimate.
Sources
Official Basketball Rules 2024: Basketball Equipment, FIBA, 2024
Key Anthropometric and Physical Determinants at the NBA Draft Combine, Cui et al., 2019
Combine Indicators of Slam Dunk Contest Finalists, Tong and Wang, 2024
A Review of Countermovement and Squat Jump Testing Methods, Petrigna et al., 2019