Quick answer
For a jump that leaves and returns to the same center-of-mass height, total airtime splits evenly around the apex. A measured 0.6-second airtime gives about 0.441 meters (17.37 inches) of vertical rise under standard Earth gravity.
This is a kinematic estimate, not a reach or dunk-height measurement. Takeoff posture, landing posture, video frame rate, surface compression, and event-detection rules can change a practical result.
How to use the calculator
- Choose whether you know total airtime or vertical takeoff speed.
- Enter the selected measurement and leave gravity at 9.80665 m/s² for an Earth-surface estimate.
- Read vertical rise, total airtime, time to apex, and the corresponding vertical speeds together.
- Compare repeated trials using the same camera angle, frame rate, surface, and takeoff/landing definition.
What each result means
- Estimated vertical rise: change in center-of-mass height from takeoff to the apex in the same-height model.
- Estimated airtime: time from takeoff to landing when both events occur at the same height.
- Time to apex: half of total airtime, or vertical takeoff speed divided by gravity.
- Initial vertical speed: upward velocity required by the model at takeoff.
- Same-height landing speed: the equal-magnitude downward speed produced by the idealized symmetric path.
Decisions this calculator helps with
Translate video airtime
Turn a measured airborne interval into an approximate vertical rise before comparing trials.
Compare takeoff speeds
See how a change in vertical velocity affects both height and time in the air.
Spot measurement sensitivity
Try nearby airtimes to see how a one- or two-frame timing difference changes the height estimate.
Keep the scenario
Share, copy, or print the inputs and results, then record the camera frame rate and event definition beside them.
Hang time and jump-height formulas
For total airtime T, vertical takeoff speed v, gravity g, and equal takeoff and landing height:
- Time to apex = T ÷ 2.
- Initial vertical speed = g × T ÷ 2.
- Vertical rise = g × T² ÷ 8.
- Airtime from vertical speed = 2 × v ÷ g.
- Vertical rise from speed = v² ÷ (2 × g).
The formulas describe vertical motion only. Horizontal speed does not change this idealized vertical result because the components are treated independently when air resistance is neglected.
Assumptions and limitations
- Takeoff and landing are treated as the same center-of-mass height. A deeper landing posture can lengthen measured airtime and overstate rise.
- Gravity is constant and air resistance is neglected. These are standard introductory projectile-motion assumptions.
- The calculator does not infer standing reach, hand height, box height, dunk clearance, force, power, or horizontal distance.
- Phone video may measure takeoff and contact only to the nearest frame. At 30 frames per second, one frame is about 0.033 seconds.
- Force plates, jump mats, optical systems, and video apps may use different thresholds. Compare results only when the event definition is consistent.
Worked hang-time examples
| Known measurement | Calculation | Estimated result |
|---|---|---|
| 0.60 s airtime | 9.80665 × 0.60² ÷ 8 | 0.441 m (17.37 in) rise; 2.942 m/s takeoff speed |
| 4.00 m/s vertical takeoff speed | 2 × 4.00 ÷ 9.80665 | 0.816 s airtime; 0.816 m (32.12 in) rise |
| 0.80 s airtime | 9.80665 × 0.80² ÷ 8 | 0.785 m (30.89 in) rise; 3.923 m/s takeoff speed |
Common mistakes when estimating hang time
- Using time to the apex as if it were total airtime; total airtime is twice as long in the same-height model.
- Measuring the first visible foot movement instead of the instant all support is lost.
- Counting landing at a lower center-of-mass position than takeoff without noting the model mismatch.
- Comparing clips recorded at different frame rates or from angles that hide floor contact.
- Treating center-of-mass rise as the same thing as reach, box height, or clearance over an object.
Hang time calculator FAQ
How do you calculate jump height from hang time?
For a jump that takes off and lands at the same center-of-mass height, time to the apex is half the total airtime. Initial vertical speed is gravity multiplied by that half-time, and rise is gravity multiplied by total airtime squared, divided by eight.
What does a 0.6-second hang time mean?
Using standard gravity and the same-height model, 0.6 seconds corresponds to about 0.441 meters, or 17.37 inches, of vertical rise and an initial vertical speed of about 2.942 meters per second.
Why can video-based jump height differ from this estimate?
Body position can change between takeoff and landing, frame rate limits the timing precision, and the measured airborne interval may not match center-of-mass motion exactly. A force plate or calibrated jump mat uses a more controlled event definition.
Does horizontal speed change the hang-time result?
Not in this idealized vertical calculation. Horizontal and vertical motion are treated independently when air resistance is neglected, so the vertical component sets airtime and rise.
Can I calculate airtime from takeoff speed?
Yes. Select vertical takeoff speed. For matching takeoff and landing height, total airtime is two times vertical speed divided by gravity.
Is this a standing reach or dunk-height calculator?
No. It estimates vertical center-of-mass rise from airtime or vertical speed. Reach, arm extension, ball control, approach technique, and takeoff posture require separate measurements.
Sources and method notes
References used for gravity and the motion model:
- NIST gives standard acceleration of gravity as exactly 9.80665 m/s².
- OpenStax describes projectile motion under gravity and the introductory approximation that neglects air resistance.
- The same-height formulas follow constant-acceleration vertical kinematics.
- Calculation method: HANG_TIME-1.0.
What can change the result most: airtime drives the estimate and is squared in the height formula, so a small timing difference can move the rise estimate noticeably.
Updated: July 22, 2026. Last reviewed: July 22, 2026.
What to do next
Repeat the measurement with the same recording setup, then compare nearby frame counts to understand timing sensitivity. Use the run race pace calculator for distance-and-time planning or the cross-country ski size calculator for equipment sizing. If the output differs from a controlled reference, report an issue with the inputs and recording frame rate.