This free fall calculator works out how long an object takes to fall from a given height and how fast it is moving when it lands, assuming it is dropped from rest and air resistance is ignored. Free fall is the motion of an object under gravity alone, and it is one of the clearest demonstrations in physics that, in the absence of air, all objects fall at the same rate regardless of their mass, so a feather and a hammer dropped together would land at the same moment. You enter the drop height and the strength of gravity, which defaults to Earth's 9.81 metres per second squared but can be changed to model the Moon or Mars, and the calculator returns the time to fall and the impact speed, also shown in kilometres per hour to make it relatable. It uses the standard results that the fall time is the square root of twice the height over gravity, and the impact speed is the square root of twice gravity times the height. Bear in mind these assume a vacuum: real falling objects are slowed by air and level off at a terminal velocity, so a skydiver does not keep speeding up forever. This is a core mechanics tool and a great way to appreciate just how quickly falling speeds build up. Enter a height to see the result straight away.
Assumes a drop from rest with no air resistance. Real objects reach a terminal velocity. Estimate only.
The calculator finds the fall time as the square root of two times the height divided by gravity, then the impact speed as gravity times that time, which is the same as the square root of two times gravity times the height. The impact speed is also converted to kilometres per hour by multiplying by 3.6.
An object dropped from 45 metres on Earth takes the square root of 2 times 45 over 9.81, about 3.03 seconds, to land, hitting the ground at roughly 29.7 metres per second, which is about 107 kilometres per hour.
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