Vertical Jump, Explained

This guide shows you how to turn a jump-mat flight time or a reach difference into a jump height in centimeters, and how to estimate peak leg power with the Sayers equation. Every formula is derived and checked against a worked example.

What the calculator gives you

A vertical jump is one number that says how high your center of mass rose above its standing position. From that single height and your body weight, you can also estimate how much power your legs produced in the push-off. There are two common ways to measure the height.

The first way is the reach method: you record how high you can touch flat-footed, then how high you touch at the top of a jump. The difference is your jump. The second way is the flight-time method: a mat or a phone app measures how long your feet are off the ground, and physics converts that time into a height.

As a hook, take the demo numbers. A touch of 285 cm from a standing reach of 230 cm is a 55 cm jump. A flight time of 560 ms gives almost exactly the same height, and an 80 kg athlete with a 55 cm jump produces roughly 4300 watts of peak power. The sections below show where each of those numbers comes from.

When to use each method

The two methods measure the same quantity but fail in different ways, so pick based on what you have and what you trust.

Reach method: Best when you have a marked wall or a Vertec device. It measures the real rise of your hand, so bent knees in the air do not inflate it. The weak point is arm extension: if you reach higher at the top than you did standing, you overstate the jump.
Flight-time method: Best with a contact mat or a validated app. It needs no wall and no reach measurement. The weak point is your landing and take-off posture, explained in the mistakes section.

Do not mix a flight time from one jump with a reach from another and expect them to match to the millimeter. Jump-to-jump variation of 2 to 4 cm is normal even for the same athlete on the same day.

The flight-time formula and why it works

When you leave the ground, only gravity acts on your center of mass (ignoring air resistance, which is negligible for a jump). The motion up and the motion down are symmetric, so half the flight time is spent rising and half falling. If total flight time is t, the time to reach the peak is t/2.

During the fall from the peak, the body drops a height h from rest under acceleration g. The constant-acceleration relation h = \frac{1}{2} g (t/2)^2 simplifies to the working formula.

h = \frac{g \cdot t^2}{8}

Here h is jump height in meters, g is gravitational acceleration (9.81 m/s²), and t is flight time in seconds. The 8 in the denominator is 2 \times 2^2: one factor of 2 from the \frac{1}{2} in the fall equation and a factor of 4 from squaring the half-time.

The formula is very sensitive because time is squared. A 5 percent error in t becomes about a 10 percent error in h. At 560 ms, a mistimed contact of just 10 ms shifts the height by about 2 cm.

The Sayers peak power equation

Height tells you what your legs achieved but not how hard they worked. The Sayers equation estimates peak power output during the push-off from jump height and body mass. It was fitted to force-plate data across many athletes.

P_{\text{peak}} = 60.7 \cdot h + 45.3 \cdot m - 2055

Here P_{\text{peak}} is peak power in watts, h is jump height in centimeters (not meters), and m is body mass in kilograms. The three constants are regression coefficients, so treat the result as an estimate with roughly \pm 10\% spread, not an exact reading.

The height in the Sayers equation is in centimeters, while the flight-time formula returns meters. Convert before you plug in: a 0.55 m jump is 55 cm. Forgetting this makes the power estimate absurdly small.

A worked example with the demo data

Reproducing the default jump

Use the tool defaults: standing reach 230 cm, jump touch 285 cm, flight time 560 ms, body weight 80 kg.

Reach-method height: 285 - 230 = 55 cm.
Flight-time height: convert 560 ms to 0.560 s, then h = \frac{9.81 \times 0.560^2}{8} = \frac{9.81 \times 0.3136}{8}.
Numerator: 9.81 × 0.3136 = 3.077. Divide by 8: 0.3846 m, which is 38.5 cm.
The two methods disagree here (55 cm versus 38.5 cm) because the demo values are independent samples, not the same jump. Real matched data would land within a few centimeters.
Sayers power from the reach height of 55 cm: P = 60.7 \times 55 + 45.3 \times 80 - 2055.
Compute each term: 60.7 × 55 = 3338.5, 45.3 × 80 = 3624. Sum minus offset: 3338.5 + 3624 - 2055 = 4907.5 W.

So the reach method gives 55 cm and about 4910 watts of peak power. If instead you feed the flight-time height of 38.5 cm into Sayers, you get 60.7 × 38.5 + 3624 - 2055 = 3906 W. The 16.5 cm height gap propagates into roughly 1000 watts, which shows why the height measurement matters more than any single coefficient.

How flight time maps to height and power

The chart below plots the flight-time formula across a realistic range. Notice the curve, not a straight line: because height goes with time squared, equal steps in time add more height at the top end.

Height rising with the square of flight time. The vertical marker sits at the demo value of 560 ms, giving 0.385 m.

The widget lets you move body weight and jump height independently and watch the Sayers power respond, so you can feel how much each input matters.

Reading and interpreting your result

A jump height means little without a reference. The table gives rough adult benchmarks. These are broad bands, not cutoffs, and they shift with age, sport and sex.

Approximate adult vertical jump benchmarks (untrained to trained)
Band	Men (cm)	Women (cm)
Below average	< 40	< 30
Average	40 to 50	30 to 40
Good	50 to 60	40 to 50
Excellent	60 to 70	50 to 60
Elite	> 70	> 60

The demo 55 cm jump sits in the "good" band for men and "excellent" for women. For training, the useful signal is your own trend, not the band label. A change of 3 cm across a training block is meaningful; a 1 cm difference between two jumps on the same day is noise.

Common mistakes

The biggest flight-time error is tucking your feet or landing with bent knees. Both extend the time in the air without raising your center of mass, so the formula reports a height you never reached. A tuck that adds 40 ms to a 560 ms flight inflates the height from 38.5 cm to about 44 cm, a fake 5.5 cm gain.

Two more traps to avoid. First, unit slips: the Sayers equation wants centimeters, so entering 0.55 instead of 55 gives a wildly wrong power. Second, reach-method inflation: if you stretch higher overhead at the top of the jump than you did while measuring standing reach, you count arm extension as jump height. Measure standing reach with the same full stretch you will use in the air.

Finally, remember the error bars. The Sayers power estimate carries about \pm 10\%, so 4908 W really means roughly 4400 to 5400 W. Do not compare two athletes whose estimates differ by less than that.

Related tools on this site

If you work across track and field events, the Decathlon & Heptathlon Points Calculator scores the standing and running events on the World Athletics tables. Sprinters correcting their marks can use the Sprint Wind & Altitude Adjuster. For basketball, where jump height feeds into scoring output, the True Shooting % Calculator turns a box score line into efficiency numbers.

Frequently asked questions

Which method is more accurate, reach or flight time?

A calibrated force plate is the reference, and reach against a marked wall is close when your standing reach is measured with full stretch. Flight-time apps are convenient but sensitive to take-off and landing form. Trust the method you can repeat cleanly.

Why do my two methods disagree?

Usually because they measured different jumps, or because you tucked your feet on the timed jump, or extended your arm more at the top than during your standing reach. Match the jumps and check your posture before assuming the tool is wrong.

Does a heavier athlete always produce more power?

The Sayers equation adds 45.3 W per kilogram, so at the same jump height, yes. But extra mass also lowers jump height for most people, so total power depends on the trade-off. Compare power at your actual measured height, not a hypothetical one.

How much can I realistically improve my jump?

This guide gives no performance promise. Trained changes across a block are commonly a few centimeters. Treat any single-session swing under about 3 cm as measurement noise rather than progress.

Should I use the estimated power for medical or clinical decisions?

No. These are educational estimates for sport and training. They are not medical advice and not a substitute for professional coaching or clinical testing.

Try it yourself in the tool