Calculate how long it takes to fall a given height, and how fast you hit the ground, in free fall without air resistance.
In free fall, the fall time (t) is determined by the fall height (h) and gravitational acceleration (g = 9.81 m/s²). The final speed (v) when the object hits the ground is found by multiplying gravitational acceleration by the fall time, or directly with v = √(2 × g × h).
These formulas assume the object is dropped from rest, i.e. with no initial speed, and ignore air resistance.
Because gravitational acceleration is the same for all objects, regardless of mass. A stone and a feather fall at the same rate in a vacuum — it's air resistance that normally makes light or large objects fall slower in practice.
Air resistance slows falling objects, especially those with a large surface area relative to their weight. In reality, objects eventually reach a constant "terminal velocity" where air resistance equals the force of gravity, which this calculator doesn't account for.
Free fall is straight-down motion with no initial speed. Projectile motion (for example throwing a ball) also has a horizontal speed component, so the motion becomes a combination of horizontal straight-line motion and vertical free fall.