Free Fall Calculator

Calculate how long an object takes to fall from a given height, or how far it falls in a given time — with final velocity.

How to use

  1. Type the height in metres or the fall time in seconds. Leave the other field empty.
  2. The missing value and the final velocity appear as you type.
  3. Change the gravity field to simulate a fall on the Moon (1.62) or Mars (3.72).

About this tool

Free fall is motion under gravity alone, with no air resistance. An object dropped from rest accelerates at g (9.81 m/s² on Earth), and the equations of uniformly accelerated motion give the height, time and final velocity. This calculator solves for whichever variable you leave empty.

In reality, air resistance limits the speed to a terminal velocity that depends on the object's shape, size and mass. A skydiver reaches about 55 m/s (200 km/h); a tennis ball about 30 m/s. The free-fall equations are a good approximation for short drops, heavy objects and vacuum, and they are the starting point for every physics textbook.

The gravity field defaults to Earth's standard value (9.81 m/s²). Change it to simulate other worlds: the Moon is 1.62, Mars 3.72, Jupiter 24.79. The equations are the same everywhere — only g changes.

The formula

h = ½gt². t = √(2h/g). v = gt. On Earth, g = 9.81 m/s².

Frequently asked questions

Why does it say "assumes no air resistance"?

Because in real life, air resistance slows the fall. The calculator gives the theoretical free-fall time in a vacuum. For light objects or long falls, the real time is longer.

Does mass affect the fall time?

In a vacuum, no — all objects fall at the same rate. In air, a heavier object reaches a higher terminal velocity and falls faster, but the free-fall equations do not include mass.

How can I simulate a fall on the Moon?

Change the gravity field to 1.62 m/s². The same height takes about 2.5 times longer to fall on the Moon.

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