The physics
Dunking is just clearance arithmetic. Add the rim height. Subtract your reach. The number you’re left with is the vertical you need to get a hand on the iron.
From there, add inches for the dunk you actually want - six for a one-hand palm, ten for a two-hander, fifteen if you want to bring it down hard or windmill.
vertical_needed = rim − reach + dunk_clearance − approach_boost
Hang time and takeoff velocity fall out of projectile motion. With gravity at 32.2 ft/s², a 28-inch vertical means you’re in the air for about 0.76 seconds and leave the ground at roughly 10.4 mph.
Frequently asked
How do I measure my standing reach?
Stand flat-footed against a wall in shoes, arm fully extended overhead, fingers straight. Mark the highest point your fingertips touch. That’s your reach. Don’t cheat with a toe lift.
Why isn’t my approach boost as big as the pros’?
Elite jumpers plant hard and convert horizontal momentum into vertical lift with very efficient mechanics. Most amateurs lose energy on a slow plant or a long last step. Plyometrics and approach drills help more than weight training alone.
What about gym rims that aren’t exactly 10 feet?
Many older outdoor rims sag a half-inch to an inch low. Some adjustable rims are set wrong. If you’re going to obsess about clearance, bring a tape measure.