Drop something and gravity does the rest. Solve for velocity, time, or distance during free fall — the same physics behind Galileo's tower experiment, worked out for you instantly.
A free fall calculator lets you instantly determine how an object behaves when falling under gravity alone, using the classic kinematic equations for constant acceleration. Enter either the height an object falls from or the time it spends falling, and the calculator computes the remaining values — fall time or height, and impact velocity — using Earth's standard gravitational acceleration of 9.81 m/s² (adjustable for other planets and moons).
Free fall is one of the most fundamental and elegant concepts in classical mechanics: it describes the motion of any object acted on solely by gravity, with no air resistance or other forces. Because gravitational acceleration is constant near a planet's surface and independent of an object's mass, all objects — from a dropped coin to a skydiver before reaching terminal velocity — accelerate downward at exactly the same rate under ideal free fall conditions, a fact famously demonstrated by Galileo's (possibly apocryphal) Leaning Tower of Pisa experiment and confirmed decades later on the airless Moon.
This calculator is useful across many contexts: physics students use it to verify homework calculations and understand kinematics, engineers use it to estimate impact forces and fall-related safety margins, and space enthusiasts use it to compare how dramatically fall times and speeds change on the Moon, Mars, or other celestial bodies with different gravitational strength. Because the tool lets you adjust gravity, it doubles as a comparative tool for exploring gravitational physics beyond Earth.
A rock climber accidentally drops a water bottle from a ledge 45 meters above the ground. Using the free-fall formula, the fall time is t = √(2 × 45 / 9.81) ≈ 3.03 seconds, and the bottle hits the ground at approximately v = 9.81 × 3.03 ≈ 29.7 m/s (about 107 km/h or 66 mph) — illustrating why falling objects, even relatively light ones, can be dangerous from significant heights due to the speed gravity builds up over just a few seconds.
The results from this calculator represent ideal free fall — motion under gravity alone with no air resistance. This is a very close approximation for dense, compact objects falling relatively short distances (a dropped tool, a stone, a person falling a few meters), but becomes progressively less accurate for lighter objects, larger surface areas, or longer fall distances where air resistance has more time and opportunity to slow the object down. When comparing your result to the reference table, notice how impact velocity grows with the square root of height rather than linearly — quadrupling the fall height only doubles the impact speed, not quadruples it, because more of the extra height is 'used up' overcoming the object's already-substantial velocity from the first portion of the fall. If you're calculating fall scenarios on other worlds, remember that changing the gravity value affects both time and velocity results proportionally — halving gravity roughly doubles fall time for a given height (since time scales with the inverse square root of gravity) while also changing the resulting impact velocity.
Enter either a height or a time (not both) — the calculator computes the rest using free-fall equations. Adjust gravity for other planets.
| Scenario | Height | Fall Time | Impact Speed |
|---|---|---|---|
| Dropped phone (waist height) | 1.5 m | 0.55 s | 5.4 m/s |
| Diving board | 3 m | 0.78 s | 7.65 m/s |
| Second-floor window | 6 m | 1.11 s | 10.89 m/s |
| Bridge (bungee height) | 30 m | 2.47 s | 24.23 m/s |
| 50-story skyscraper | 150 m | 5.53 s | 54.25 m/s |