Jump testing
Vertical jump calculator
Count how many frames an athlete spends in the air and this calculator converts that flight time into jump height using h = g × t² ÷ 8. A jump with 0.50 seconds of flight time (120 frames at 240 fps) works out to about 30.7 cm (12.1 in).
The rate the video was captured at, not the playback rate. iPhone slow motion is 120 or 240 fps.
From the first frame both feet are off the ground to the first frame a foot touches down.
Jump height
30.7cm
- Flight time
- 0.500 s
- One frame lasts
- 4.2 ms
- Range for ±1 frame
- 30.1–31.2 cm
How to measure a vertical jump on video
- Film from the side with the camera still and level with the athlete's feet, using the highest frame rate available (120 or 240 fps slow motion).
- Step frame by frame to the takeoff frame: the first frame where both feet have left the ground.
- Keep stepping to the landing frame: the first frame where either foot touches the ground again.
- Enter the number of frames between takeoff and landing and the frame rate the video was captured at.
- Measure several jumps and use the best or the average, depending on what you are tracking.
Formula
h = g × t² ÷ 8
t is flight time in seconds (frames ÷ frame rate) and g is 9.81 m/s². The athlete rises for half of the flight and falls for the other half, so the fall from the peak lasts t ÷ 2 and covers ½ × g × (t ÷ 2)², which simplifies to g × t² ÷ 8.
Flight time to jump height
| Flight time | Frames at 240 fps | Jump height (cm) | Jump height (in) |
|---|---|---|---|
| 0.30 s | 72 | 11.0 | 4.3 |
| 0.35 s | 84 | 15.0 | 5.9 |
| 0.40 s | 96 | 19.6 | 7.7 |
| 0.45 s | 108 | 24.8 | 9.8 |
| 0.50 s | 120 | 30.7 | 12.1 |
| 0.55 s | 132 | 37.1 | 14.6 |
| 0.60 s | 144 | 44.1 | 17.4 |
| 0.65 s | 156 | 51.8 | 20.4 |
| 0.70 s | 168 | 60.1 | 23.7 |
| 0.75 s | 180 | 69.0 | 27.2 |
| 0.80 s | 192 | 78.5 | 30.9 |
Common mistakes
- Landing with bent knees or hips, or tucking the legs, adds time in the air and overstates the jump. The method assumes the athlete lands in the same extended position they took off in.
- Using the playback frame rate instead of the capture frame rate. iPhone slow motion is recorded at 240 fps but plays back at 30 fps, so always enter 240.
- Filming at 30 fps. One frame of error at 30 fps changes a typical jump by about 4 cm, compared with about 0.5 cm at 240 fps.
- Comparing flight-time results directly with jump-and-reach or force plate numbers. Different methods measure slightly different things, so compare like with like.
Frequently asked questions
How accurate is the flight time method for vertical jump?
With a high frame rate and consistent landing technique it is a repeatable field method, and phone-based flight-time measurements have shown good agreement with force plates in published studies. Precision is limited by frame rate: at 240 fps each frame is about 4 milliseconds.
What frame rate do I need to measure a vertical jump?
Use 120 fps or higher. At 240 fps a one-frame counting error changes a typical jump by about half a centimeter; at 30 fps the same error is about 4 centimeters.
Does this work for countermovement, squat, and drop jumps?
Yes. The flight-time method works for any jump that takes off from and lands on the same surface in the same body position. For drop jumps, also time ground contact with the frames to time calculator; jump height divided by contact time gives the reactive strength index (RSI).
Related terms
Count frames on your iPhone or iPad
KineVision plays video in slow motion, steps through it frame by frame, and includes a stopwatch, angle tools, and side-by-side comparison for coaching.
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