⚙️

Free Fall Calculator

Free fall calculator — fall time, impact velocity, and speed from any drop height and gravity, with an animated drop.

Free fall from a height under gravity (ignoring air resistance). Leave the initial speed at 0 for a simple drop, or set it for a downward throw.

released from rest, gravity accelerates the object; a greater drop height means a longer fall and a faster impact

Drop height h (m)

Initial speed v₀ (m/s)

Gravity g (m/s²)

Earth g = 9.81, Moon = 1.62, Mars = 3.71 m/s².

Enter a drop height to see the fall time, impact velocity, and the animated drop.

Loading…

Everyday Uses

Fall time, speed or drop height

Find fall time, impact speed or drop height from any one of the others.

Safety assessment

Estimate the impact velocity of an object falling from a working height.

Understanding terminal velocity

See where the idealised equations stop matching reality.

Other worlds

Compare fall times on the Moon or Mars against Earth.

Site safety

Estimate the impact speed of a tool dropped from scaffolding.

Comparing worlds

Same drop, different gravity — Earth, Moon and Mars side by side.

Frequently Asked Questions

What is free fall?

Motion under gravity alone, with air resistance neglected. On Earth that means a constant downward acceleration of about 9.81 m/s² regardless of mass — the point Galileo made and the Apollo 15 hammer-and-feather demonstration confirmed on the Moon. Objects speed up by roughly 9.81 m/s for every second of fall, so after three seconds a dropped object is moving at about 29 m/s.

Why doesn't mass affect the rate of fall?

Because gravitational force is proportional to mass, and so is resistance to acceleration. A heavier object experiences more force but needs more force to accelerate at the same rate, and the two cancel exactly. In real air, mass does matter indirectly — heavier objects overcome drag more easily relative to their weight, which is why a feather falls slowly and a hammer does not.

What are the free-fall equations?

Velocity equals initial velocity plus g times time. Distance equals initial velocity times time plus half g times time squared. Velocity squared equals initial velocity squared plus twice g times distance — useful when you know the height but not the duration. Dropping from rest simplifies these considerably, since the initial velocity terms vanish.

What is terminal velocity and when does it matter?

The speed at which drag equals weight, so acceleration stops. A skydiver in a spread position reaches roughly 55 m/s, about 195 km/h, in around 12 seconds; head-down it is far higher. Free-fall equations are accurate for short drops of a few metres but increasingly wrong beyond that, because drag grows with the square of speed and eventually dominates.

Does g change from place to place?

Slightly. It is about 9.78 m/s² at the equator and 9.83 at the poles, because Earth bulges and rotates. It also falls with altitude — about 0.3% lower at the top of Everest. Other bodies differ enormously: 1.62 on the Moon, 3.71 on Mars, 24.79 on Jupiter. Using 9.81 is fine for terrestrial problems; a stated local value matters in precision work.

How long does something take to fall a given height?

Rearranging the distance equation for a drop from rest gives time equal to the square root of twice the height divided by g. Ten metres takes about 1.43 seconds; 100 metres about 4.5. Note the square root — it is why quadrupling the height only doubles the fall time, and why the first metre of a fall takes far longer than the tenth.

How to calculate free fall time and speed

From rest, an object falls h = ½gt², so the time is √(2h ÷ g) and the impact speed is √(2gh). These ignore air resistance, which matters for anything light or falling far.

Free fall examples (Earth, g = 9.81 m/s²)

10 m: 1.43 s — 14.01 m/s (50.4 km/h)About a three-storey drop.
20 m: 2.02 s — 19.81 m/s (71.3 km/h)
50 m: 3.19 s — 31.32 m/s (112.8 km/h)
100 m: 4.52 s — 44.29 m/s (159.5 km/h)Real skydivers never reach this: terminal velocity caps them near 195 km/h.