Free tool
Vertical jump calculator
Get your jump height from flight time or a reach test, see how it rates, and work out your reactive strength index (RSI) from a drop jump.
height = 9.81 × t² ÷ 8
The maths
How it works
Flight time
You rise and fall for the same time, so jump height follows from the time you spend in the air: h = g × t² ÷ 8, with g = 9.81 m/s². A 560 ms flight time is about 38.5 cm (15.1 in). Jump mats and phone apps that time the jump work this way. Land the way you took off, with straight legs: tucking adds air time and inflates the result.
Reach test
Jump touch minus standing reach. It is the classic Vertec or wall test. It usually reads a little higher than flight time, because you reach with one arm and lift the shoulder.
Reactive strength index
RSI is jump height in metres divided by ground contact time in seconds, from a drop jump. It shows how well you turn a fast landing into a high jump, which matters for sprinting and jumping.
Norms
How good is your vertical?
General ratings for adults. Trained jumpers and athletes in jumping sports usually sit well above these.
| Rating | Men | Women |
|---|---|---|
| Excellent | 28+ in71+ cm | 24+ in61+ cm |
| Very good | 24–28 in61–71 cm | 20–24 in51–61 cm |
| Above average | 20–24 in51–61 cm | 16–20 in41–51 cm |
| Average | 16–20 in41–51 cm | 12–16 in30–41 cm |
| Below average | 12–16 in30–41 cm | 8–12 in20–30 cm |
| Poor | Under 12 inUnder 30 cm | Under 8 inUnder 20 cm |
What is a good RSI?
| Drop jump RSI | Rating |
|---|---|
| Below 1.5 | Low |
| 1.5 to 2.0 | Average |
| 2.0 to 2.5 | Good |
| 2.5 to 3.0 | Very good |
| Above 3.0 | Excellent |
From a 30 to 40 cm box. Values depend on drop height and on how contact time is measured.
FAQ
Questions
How do I calculate my vertical jump?
Measure your standing reach, jump and touch as high as you can, and subtract the two. Or time how long you are in the air and use height = 9.81 × t² ÷ 8, with t in seconds. Filming the jump in slow motion gives you the flight time.
How do I convert flight time to jump height?
Square the flight time in seconds, multiply by 9.81 and divide by 8. That gives the height in metres. A flight time of 0.56 s is 9.81 × 0.3136 ÷ 8 = 0.385 m, about 38.5 cm or 15.1 in.
Is a 30 inch vertical good?
Yes. 30 inches (76 cm) is above the excellent line on general adult norms for both men and women. Jumping athletes such as volleyball and basketball players are often higher.
Why does my flight time result differ from my reach test?
Bending your knees or tucking your legs before landing adds air time and raises a flight time result. Reaching with one arm and shrugging the shoulder raise a reach test result. Use the same method every time when you track progress.
What is a good RSI?
For a drop jump from a 30 to 40 cm box, an RSI of 2.0 to 2.5 is good and above 3.0 is excellent. Values depend on the drop height and on how ground contact time is measured.
How do I measure ground contact time for RSI?
Use a contact mat, a force plate or a slow-motion video where you count frames from landing to takeoff. At 240 frames per second each frame is about 4 ms. TrackJump measures contact time and RSI from your iPhone camera.
TrackJump for iPhone
Measure it with your iPhone.
TrackJump measures jump height, contact time and RSI with your iPhone camera, keeps a replay of every jump and tracks your progress. No extra hardware.
See how TrackJump works