Dunk Calculator: watch your jump before you take it

Dunk calculator guide · Updated 23 October 2026

How high do you need to jump to dunk?

Most players need a running jump between 25 and 36 inches to dunk on a 10 foot rim. Your exact number depends on your standing reach, the dunk you want and the ball you use.

The calculator at the top of this page works it out for your body. Here is the same math for one player, step by step.

How to use the dunk calculator

1. Add your body. Set your height, then your standing reach. If you have no tape measure, pick Estimate it and add your wingspan if you know it.
2. Add your jump. Enter your standing vertical, or pick the highest thing you can touch on a 10 foot hoop.
3. Pick your goal. Choose the dunk, the ball and the rim height you want.
4. Watch the jump. Press Take a jump to see one real attempt, or Take 10 to see how many land.

Tap any ? button on the page to see a word in plain language with your own number. Tap any number in the panel to type it exactly, like 6’4 or 193 cm.

The dunk formula

Jump needed equals rim height, plus clearance for the ball, plus any palm allowance, minus your standing reach.

Clearance grows with harder dunks and bigger balls. The palm allowance only applies to one hand dunks. It adds up to 2 inches if your hand is too small to palm the ball.

Here is the formula with your own numbers. It updates as you move the sliders.

Jump needed by height

This table uses the dunk, ball and rim you picked, so it changes with the calculator. It estimates reach as 1.33 times height. Arm length changes from person to person, so a measured reach is more accurate. Your row is highlighted.

What vertical you need to dunk at your height

Each answer below uses an average reach of 1.33 times height, a one hand dunk, a men’s ball, a hand big enough to palm it and a 10 foot rim. For that setup, the dunk line is 126 inches.

How much room each dunk needs above the rim

Harder dunks need your hand higher above the rim, and smaller balls need less room. The table shows the room each dunk needs with each ball. Your pick is in orange.

These values assume a hand big enough to palm the ball. A smaller hand adds up to 2 inches for one hand dunks.

Why your reach matters more than your height

Two players of the same height can have very different reach. Long arms and wide shoulders lift your fingertips higher before you even leave the floor.

Spud Webb won the 1986 NBA Slam Dunk Contest at 5 feet 7 inches tall. A big jump can make up for a short frame.

Add your wingspan in the calculator to sharpen your reach estimate. Every extra inch of reach is one inch less you need to jump.

Why you dunk some days and miss on others

Your jump changes a little every time, even on the same day. The calculator assumes each jump can land about 3.5 percent above or below your average.

The make rate shows how many jumps out of 100 would clear the dunk line.

Press Take 10 under the court to watch this happen.

How your weight changes your jump

Your legs lift your whole body. If your legs stay just as strong and you weigh less, you take off faster and rise higher.

Move the weight slider to see your own number, and watch your player get leaner or heavier. The calculator treats a weight change as body fat. Adding muscle can raise your jump instead.

Hang time and takeoff speed

Hang time comes straight from your jump height. Gravity pulls everyone down at the same rate. A higher jump always gives you more time in the air.

Only a small part of that time is spent above the rim. The calculator shows your own time above the rim under Hang time.

How to close the gap

The Fastest ways to close the gap card above ranks these changes for your body. These are the main ones.

• Train your jump. Across 26 studies, plyometric training raised countermovement jump height by 8.7 percent on average.
• Build leg strength. Squats and lunges help your legs push harder. The calculator shows what 10 percent more push off the floor would add for you.
• Drop extra body fat. The weight example above shows what 10 lb less can add.
• Use a running start. Most players jump a few inches higher off a run up than from standing.
• Start with a smaller ball. Dunk a tennis ball first, then a volleyball, then a smaller basketball, then a men’s ball.
• Lower the rim. Your Rim you dunk today number shows the hoop height to start on.

How long it takes to learn to dunk

It depends on how far you are from the dunk line. A player 2 inches short gets there sooner than a player 10 inches short.

The When you’ll dunk chart gives your own estimate. It starts from the average gain in plyometric studies and slows down as you get closer to your limit. Real progress is often faster at the start.

How to measure your reach and vertical at home

1. Stand side on to a wall with both heels flat on the floor.
2. Reach one arm straight up and mark where your fingertips touch. Measure from the floor to the mark to get your standing reach.
3. Chalk your fingertips. Jump from standing and slap the wall as high as you can.
4. Measure from the floor to the highest slap. Take away your standing reach to get your standing vertical.
5. Repeat with two or three steps of run up to find your running jump.

No wall to mark? In the calculator, pick Use what I can touch. Then choose the highest thing you can reach on a 10 foot hoop.

How the dunk calculator works

• Rim, ring and backboard sizes follow the NBA rules. The rim sits 10 feet high. The ring is 18 inches across, and the backboard is 6 feet wide.
• Clearance starts at 6 inches for a one hand dunk with a men’s ball. Harder dunks get more, and smaller balls get less.
• Hand spans below 9 inches add up to 2 inches for one hand dunks with a men’s ball.
• A running start adds 4 inches unless you set your own number.
• Each jump can land about 3.5 percent above or below your average, plus 0.4 inches for timing.
• Takeoff speed and hang time use gravity at 9.81 meters per second, each second.
• Takeoff power uses the jump power equation published in Medicine and Science in Sports and Exercise.
• Weight changes keep your leg force the same, pushed over about a quarter of your height.
• The training projection uses an average gain of 8.7 percent and slows over time. That figure comes from a review in the British Journal of Sports Medicine.

The 3D player follows your exact jump height, takeoff speed and hang time. The body movement is a model, so use the numbers to plan your training.