Find fall time, impact velocity or drop height, with gravity for Earth, the Moon or Mars — air resistance excluded.
Air resistance is excluded: real falls through air are slower, especially for light objects and long drops. Assumes starting from rest.
solved value
How to use this tool
Pick whether you know the drop height, the fall time, or the impact velocity.
Choose Earth, the Moon or Mars — the same drop takes much longer where gravity is weaker.
The solved value is shown big, with time, velocity, height and the impact speed in km/h.
Real falls through air are slower than this ideal calculation, especially for light objects.
Formula & worked example
Dropping from 20 m on Earth: time = √(40 ÷ 9.81) = 2.019 s and impact velocity = √(2 × 9.81 × 20) = 19.81 m/s (71.3 km/h). On the Moon the same drop takes 4.97 s and hits at just 8.05 m/s.
Limitations — read this before you rely on it
This is ideal free fall: no air resistance, starting from rest, constant gravity, and a drop small compared with the planet’s radius. Air drag limits real falls to a terminal velocity (about 53 m/s for a human belly-down), so long real falls are much slower than this calculation.
Frequently asked questions
About 14.0 m/s (50.4 km/h) after 1.43 s on Earth — which is why even short falls are dangerous.
Gravity there is only 1.62 m/s², about one-sixth of Earth’s, so the same height takes about 2.5 times longer.
Not in a vacuum: a hammer and a feather fall together. In air, shape and mass matter a lot — that is the air-resistance caveat.
The speed where air drag balances gravity, so you stop accelerating — roughly 53 m/s (190 km/h) for a skydiver belly-down.
Only if it starts from rest. For an object thrown downward or upward, add the initial velocity to the equations.