Dunk Calculator

What Actually Decides Whether You Can Dunk

Height gets all the attention, but the number that really matters is standing reach: how high your fingertips get when you stand flat-footed with one arm stretched straight up. Two players who are both 6 feet tall can have standing reaches several inches apart because of arm length and shoulder width, and that difference comes straight off the jump they need. The other two pieces are fixed by the court — a regulation rim sits 10 feet (304.8 cm) off the floor — and by what you're trying to do. Brushing the rim needs no extra height at all; a real dunk needs your hand high enough to get the ball over the rim and push it down, which is usually taken as about 6 inches (15 cm) above it.

Step by Step: Getting Accurate Inputs

Pick feet-and-inches or centimeters, then enter your height. If you can, measure standing reach properly: stand side-on to a wall in bare feet, reach up with your dominant arm as high as you can without lifting your heels, and mark the tip of your middle finger. Leave it blank and the calculator estimates it from height. For your vertical, chalk your fingers or use a sticky note, jump from a standstill (or with your usual approach, if that's how you'd dunk) and measure the mark minus your standing reach. Rim height and clearance are pre-filled with standard values; lower the rim for an adjustable hoop, or raise the clearance if you have small hands and need to get well above the rim to control the ball.

The Formula Explained

Vertical to touch the rim = rim height − standing reach. Vertical to dunk = rim height + clearance − standing reach. When standing reach isn't entered, it's estimated as height × 1.33. That ratio comes from NBA Draft Combine measurements, where the median player's standing reach is about 1.335 times their height and roughly half of all players fall between 1.32 and 1.35. The gap is simply the dunk requirement minus your current vertical: a positive number is how much you still need to add, a negative one is how much room you have to spare.

A Real Example

A 6'0" player (72 inches) with no measured reach gets an estimated standing reach of 72 × 1.33 = 95.76 inches, just under 8 feet. Against a 10-foot rim (120 inches), touching it takes 120 − 95.76 = 24.24 inches of vertical. Dunking with 6 inches of clearance takes 126 − 95.76 = 30.24 inches. With a current vertical of 26 inches, this player can already touch the rim with about 1.8 inches to spare but still needs roughly 4.2 more inches of jump to dunk. In metric, a 183 cm player gets an estimated reach of 243.4 cm, needs 61.4 cm to touch a 304.8 cm rim and 76.4 cm to dunk with 15 cm clearance — a 60 cm vertical leaves a gap of about 16.4 cm.

Edge Cases to Watch For

The 1.33 estimate comes from basketball prospects, a group selected partly for long arms, so if your arms are shorter than average the estimate may flatter you by an inch or two — a measured reach always beats the estimate. Running verticals are typically several inches higher than standing ones, so compare like with like: if you plan to dunk off a run-up, measure your vertical the same way. Clearance depends heavily on hand size; players who can palm the ball comfortably can dunk with less, while two-handed dunks or anyone who can't grip the ball will usually need more. Finally, touching the rim and dunking in a game are different things — fatigue, defenders, and ball control all eat into the margin, so a vertical that only just clears the requirement in practice may not hold up on the court.