Free Fall Calculator

Free fall is the motion of an object falling solely under the influence of gravity, with no air resistance or other forces acting on it. In free fall, every object accelerates downward at the same rate regardless of its mass. Near Earth's surface this acceleration is approximately 9.81 m/s², a value defined in the International System of Units (SI) and published in NIST SP 330.

This calculator assumes a vacuum, meaning it ignores air resistance. In reality, air resistance creates a drag force that opposes motion. As a falling object speeds up, drag increases until it equals the gravitational force, at which point acceleration stops and the object reaches terminal velocity. For dense, compact objects over short distances the vacuum formula is a very close approximation. For lighter or larger objects, or longer falls, air resistance becomes significant.

Terminal velocity is the constant speed reached when drag equals the gravitational pull on a falling object. It is not calculated here because it depends on the object's drag coefficient and cross-sectional area, which vary by object. A typical skydiver reaches roughly 53 m/s (190 km/h) in a spread-eagle position. This calculator models the ideal vacuum case only.

Galileo Galilei famously argued (and reportedly demonstrated) that objects of different masses fall at the same rate when air resistance is absent, contradicting the Aristotelian view that heavier objects fall faster. This was later confirmed precisely by Newton's laws. The modern demonstration is the feather-and-hammer drop performed on the Moon during the Apollo 15 mission in 1971, where there is no atmosphere.

This calculator uses g = 9.80665 m/s², the standard acceleration of gravity defined by the International Bureau of Weights and Measures (BIPM) and published in NIST SP 330. Local gravity varies slightly with latitude and altitude, but 9.80665 m/s² is the internationally agreed standard value used in engineering and physics calculations.