Free Fall Calculator
Calculate falling time and speed
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Free Fall Calculator helps you calculate falling time and speed without a spreadsheet. Type Height (m) and Gravity (m/s²) into Free Fall; each keystroke re-runs the math. The answer from Free Fall arrives with its working attached. Free Fall shines when speed matters. Nothing typed into Free Fall leaves your device or the tab. Free Fall sits in the Science section next to free online free fall calculator and free fall calculator. Free Fall goes from question to answer fast. Start with Free Fall; the first number takes seconds.
What the defaults give
A fall of 100 m at g = 9.8 m/s² takes 4.52 seconds.
The impact speed is 44.27 m/s, roughly 159 km/h — before any air resistance is considered.
The formulas
Time: t = √(2h ÷ g)
Speed: v = √(2gh)
√(2 × 100 ÷ 9.8) = 4.517 s; √(2 × 9.8 × 100) = 44.27 m/s.
Worked examples
1 m → 0.45 s, 4.43 m/s
10 m → 1.43 s, 14.0 m/s
100 m → 4.52 s, 44.3 m/s
1,000 m → 14.3 s, 140 m/s
Why time scales with the square root
Distance grows with the square of time, so time grows with the square root of distance. Quadrupling the height only doubles the fall time, while the impact speed doubles with it. That non-linearity is why a fall from twice the height is not twice as dangerous: the energy at impact is proportional to the square of the speed, so doubling the drop quadruples the energy.
Where the vacuum answer breaks down
- Drag. Air resistance grows with the square of speed, so the real time is longer and the real impact speed lower — noticeably so above about 100 m.
- Terminal velocity. A human in a spread-eagle position tops out around 55 m/s, so long falls stop accelerating entirely.
- Shape and mass. A skydiver in a head-down position reaches over 90 m/s, while a feather never gets close.
- g is not constant. It falls with altitude, which matters for orbital-scale heights but not for a 100 m drop.
The vacuum model is the right starting point: it gives the maximum possible speed and the shortest possible time, which is often exactly the bound you want.
The vacuum answer is a bound, not a prediction: 4.52 seconds and 44.27 m/s are the shortest time and highest speed possible for a 100 m drop, and air resistance makes both less extreme. Drag grows with the square of speed, so the effect is small for a stone and large for a feather, and a person reaches terminal velocity near 55 m/s. Energy at impact scales with the square of speed, which is why doubling the height quadruples it.
Frequently Asked Questions
How long does a 100 m fall take?
About 4.52 seconds, ignoring air resistance, from the square root of twice the height divided by gravity.
What speed do you hit at 100 m?
About 44.27 m/s, close to 159 km/h in a vacuum. Air resistance reduces both the speed and increases the time.
Does weight affect falling speed?
Not in a vacuum. All objects accelerate at the same rate; mass matters only through drag, where a heavier object is slowed less.
What is terminal velocity for a person?
Roughly 55 m/s in a belly-to-earth position, higher in a head-down dive. It is the point where drag equals weight.
Why is the fall time not proportional to height?
Because distance depends on the square of time. Four times the height is only twice the fall time.
Does gravity change with height?
Slightly, but not measurably for a fall of a few hundred metres. It matters for satellites and long trajectories.
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