Free dunk calculator
Find out if you can dunk in two seconds. Enter your standing reach (or height) and your vertical jump, and the dunk calculator returns the exact vertical you need, whether you can dunk a regulation rim, and your hang time — with how much vertical you need by height, standing reach explained, and how to jump higher, updated live, as you type.
On this page15 sections
Uses a 10 ft (120 in) regulation rim and ~6 in of ball clearance. See rim height and clearance
Results are estimates. Consult a professional.
Can I dunk? What the dunk calculator tells you
A dunk — a slam dunk — is a basketball shot where you jump high enough to put the ball down through the rim from above with your hand at or over the level of the hoop. Whether you can do it comes down to one number: how high your fingertips reach at the top of your jump versus the 10-foot rim. This dunk calculator works that out instantly from your standing reach and vertical jump, and tells you the exact vertical you still need.
The key insight most people miss: dunking is a reach problem first, and a jump problem second. Two players the same height can need a vertical that differs by five inches or more, purely because of arm length. That is why the calculator works from your standing reach — your flat-footed fingertip reach — not your height alone.
How to calculate the vertical you need to dunk
There is one formula behind the whole calculation. To dunk, your reach at the top of your jump has to clear the rim with enough room to push the ball through — so you work out the target reach, then subtract what you already reach standing still.
- Measure your standing reach. Stand flat against a wall, raise one arm fully overhead, and mark the highest point your fingertips reach without jumping.
- Set the target reach. On a regulation rim that is 120 in (the 10-foot rim) plus about 6 in of clearance — roughly 126 in, or 10 ft 6 in.
- Subtract. Target reach minus your standing reach is the vertical jump you need. If your current max vertical already meets it, you can dunk.
A worked example using the dunk calculator
Marcus has a standing reach of 90 inches (7 ft 6 in) and a max vertical of 30 inches. He wants to know whether he can dunk on a regulation rim — and if not, how close he is. Here is exactly how the calculator works through it.
Step 1 — Find the target reach
The rim is 120 in (10 ft). Add 6 in of clearance to get the ball cleanly over and down: the target reach is 126 in (10 ft 6 in). That is the height his fingertips must reach at the peak of the jump.
Step 2 — Subtract his standing reach
126 in target reach minus his 90 in standing reach leaves a gap of 36 inches. That is the vertical jump Marcus needs to dunk.
| Measurement | Value |
|---|---|
| Rim height | 120 in (10 ft) |
| Ball clearance | +6 in |
| Target reach | 126 in |
| Standing reach | −90 in |
| Required vertical | 36 in |
Step 2 result: a 36-inch vertical is required to dunk with a 90-inch standing reach.
Step 3 — Compare with his current vertical
His max vertical is 30 in, but he needs 36 in — so he is 6 inches short. Not yet, but within reach of a dedicated training block. If his vertical climbs to 36 in he reaches exactly 126 in and can dunk, with about 0.86 seconds of hang time; at 40 in he clears the rim with room to spare (about 0.91 seconds airborne).
How much vertical you need to dunk, by height
Because standing reach tracks height (roughly height × 1.33), you can sketch the vertical most people need at each height. The table below assumes an average-arm standing reach and the 126-inch dunk target. Treat it as a guide — your own standing reach is what actually decides it, so measure it and let the calculator do the exact sum.
| Height | Typical standing reach | Vertical needed to dunk |
|---|---|---|
| 5 ft 6 in (66 in) | ~88 in | ~38 in |
| 5 ft 9 in (69 in) | ~92 in | ~34 in |
| 6 ft 0 in (72 in) | ~96 in | ~30 in |
| 6 ft 3 in (75 in) | ~100 in | ~26 in |
| 6 ft 6 in (78 in) | ~104 in | ~22 in |
| 6 ft 9 in (81 in) | ~108 in | ~18 in |
Estimates only, using standing reach ≈ height × 1.33 and a 126-inch (10 ft 6 in) dunk target. Long-armed players need less; short-armed players need more.
For reference, most people who can dunk a regulation rim have a vertical in the 28–34 inch range, with shorter players needing more and taller players needing less. A 40-inch vertical is elite — comparable to NBA-combine territory.
Standing reach explained (and why it beats height)
Standing reach is the single most important number in this calculator. It is how high your fingertips touch when you stand flat-footed and stretch one arm straight up — and it already bakes in your arm length, shoulder mobility, and how high you can shrug. Two 6-foot players can have standing reaches four or five inches apart, which is the difference between needing a 28-inch and a 33-inch vertical.
- Stand flat against a wall, heels and back touching it, feet flat on the floor.
- Reach one arm straight up as high as you can — shrug the shoulder, fully extend the fingers.
- Mark the highest fingertip point and measure from the floor. That is your standing reach.
If you cannot measure it, the calculator estimates it from your height with the average ratio, but the estimate can be off by several inches for unusually long or short arms — so a wall measurement is always worth the 30 seconds. You can also compare yours against typical figures with the height comparison calculator.
Rim height and ball clearance
A regulation basketball rim sits exactly 10 feet (120 inches, 3.05 m) off the floor — the same height in the NBA, college, high school, and FIBA play. That is the number the calculator uses by default, but you can lower it for a youth or adjustable hoop (many youth rims are set at 8 or 9 feet).
Touching the rim is not the same as dunking. To put the ball down through the hoop your hand has to clear the rim, so you need extra room above it — about 6 inches of clearance is the common default, making the real dunk target roughly 126 inches (10 ft 6 in). Players with bigger hands who can palm and control the ball can dunk with a touch less clearance; a two-handed or windmill dunk needs more.
| Rim setup | Rim height | Dunk target (with 6 in clearance) |
|---|---|---|
| Regulation (NBA / FIBA / HS) | 120 in (10 ft) | 126 in |
| Youth / adjustable | 108 in (9 ft) | 114 in |
| Youth / mini | 96 in (8 ft) | 102 in |
Lowering the rim drops the target reach inch-for-inch — which is why a 9-foot rim is so much more dunkable.
How to increase your vertical jump
If the calculator says you are a few inches short, those inches are trainable. A vertical jump is a mix of strength, power, and technique — and for most people who are not already explosive, the fastest gains come from getting stronger and lighter, then learning to express that power quickly.
- Build lower-body strength. Squats, deadlifts, and lunges raise the force you can put into the ground — the foundation everything else sits on.
- Train explosive power. Plyometrics — box jumps, depth jumps, broad jumps — teach your muscles to fire fast, converting strength into a quicker, higher jump.
- Improve jump technique. A good penultimate step, arm swing, and hip extension can add inches with no new strength at all.
- Lose excess body weight. Every pound you are not carrying is less to launch; a leaner athlete jumps higher at the same strength level.
- Recover and be consistent. Vertical gains come over months of regular, progressive work, not a single session — rest lets the adaptations stick.
The shortest dunkers (yes, short players can dunk)
Being tall makes dunking easier, but it is not a requirement — plenty of players well under six feet have thrown one down, on the back of an enormous vertical jump. The shorter you are, the bigger the vertical you need, which is exactly what the by-height table shows.
| Player | Height | Note |
|---|---|---|
| Spud Webb | 5 ft 7 in | Won the 1986 NBA Slam Dunk Contest at 5 ft 7 in — the classic proof short players can dunk. |
| Nate Robinson | 5 ft 9 in | Three-time NBA Slam Dunk Contest champion. |
| Muggsy Bogues | 5 ft 3 in | The shortest player in NBA history; reportedly able to touch the rim and dunk in practice. |
Shorter dunkers compensate with elite verticals — Spud Webb's was reported around 42–46 inches.
The takeaway: if you are short and the calculator shows a 38-inch-plus requirement, it is steep but not impossible — it is the same target the famous short dunkers cleared. Measure your standing reach, set a realistic vertical goal, and train toward it.
Common dunk questions
How high do I need to jump to dunk?
It depends on your standing reach. Subtract your flat-footed fingertip reach from about 126 inches (the 10-foot rim plus 6 inches of clearance). For an average-armed 6-footer that is roughly a 30-inch vertical; most people who dunk a regulation rim have a vertical in the 28–34 inch range.
Can short people dunk?
Yes. Although being tall makes it much easier to dunk a basketball, some people have proved that even short players can perform a slam dunk — Spud Webb won the NBA dunk contest at 5 ft 7 in. Shorter players simply need a much bigger vertical jump.
Why does standing reach matter more than height?
Because dunking is about how high your hand reaches, not how tall you are. Arm length, shoulder mobility, and how high you can shrug all feed into standing reach, so two people the same height can need verticals that differ by five inches or more.
How high is a basketball rim?
A regulation rim is exactly 10 feet (120 inches, 3.05 m) off the floor in the NBA, college, high school, and FIBA. To dunk you need to clear it by about 6 inches so the ball goes down cleanly, making the real target roughly 126 inches.
How this calculator works and sources
This dunk calculator applies the standard dunk identity exactly: required vertical = (rim height + clearance) − standing reach, and you can dunk when your max vertical meets it. Hang time uses the projectile formula t = 2 × √(2h ÷ g) with g = 9.81 m/s², the jump height converted to metres. The 10-foot rim is the official regulation height; the ~6-inch clearance and the standing-reach-from-height ratio (≈ 1.33) are common conventions used across dunk calculators. The maths runs entirely in your browser — nothing you enter is sent anywhere.
Omni Calculator — Dunk Calculator (required vertical leap and hang-time formulas).The Hoops Geek — Dunk Calculator (rim clearance and how-to-dunk guidance).Frequently asked questions about the free dunk calculator
About this dunk calculator
This dunk calculator runs entirely in your browser. The measurements you type never leave your device — nothing is sent to a server, logged, or shared. It applies the standard dunk identity (required vertical = rim height + clearance − standing reach) on a 10-foot regulation rim and updates instantly on every change.
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