How it works
In free fall, every object accelerates downward at g ≈ 9.81 m/s², regardless of its mass — Galileo's great insight. A hammer and a feather fall together on the Moon; on Earth only air resistance separates them.
Fall time grows with the square root of height: falling 4× higher takes only 2× longer, but you hit the ground 2× faster.
A 10 m drop (a 3-storey window) takes just 1.43 seconds and ends at 50 km/h — about the speed of a serious urban car crash.
Worked examples
Free-fall distance at a given time
The distance fallen is d = ½·g·t². After 1 s an object has dropped ½ × 9.81 × 1² ≈ 4.9 m; after 2 s ≈ 19.6 m; after 3 s ≈ 44.1 m. Because distance scales with t², each extra second adds more than the last — the third second alone covers 24.5 m.
The '120 mph free fall' figure
120 mph is a skydiver's terminal velocity, not a pure free-fall result. It equals about 193 km/h or 54 m/s — the speed at which air drag balances gravity for a belly-to-earth skydiver, so they stop accelerating rather than falling ever faster. Drag-free, reaching 54 m/s would take only ~5.5 s and 150 m; in real air a skydiver approaches it gradually over ~10–12 s. This calculator gives the ideal drag-free numbers; use the terminal-velocity calculator for the drag-limited speed.
Use it in real life
Home safety: understanding that a fall from 3 m already means hitting the ground at 28 km/h explains why ladder falls are a leading cause of serious home injuries.
Estimating depth: drop a stone into a well and count seconds — depth ≈ 4.9 × t². Two seconds means roughly 20 metres.
Amusement parks: drop towers are pure free-fall physics; a 60 m tower delivers about 3.5 seconds of weightlessness and a 124 km/h peak.
Frequently asked questions
Do heavy objects fall faster than light ones?
Not in a vacuum — all objects accelerate at the same rate g. In air, heavier and denser objects are less affected by drag, so in practice a bowling ball beats a balloon.
How fast does a human fall after 3 seconds?
Ignoring air resistance, v = g·t ≈ 29 m/s (106 km/h) after 3 seconds, having fallen about 44 m. Real skydivers reach a terminal velocity near 200 km/h where drag balances gravity.
What does this calculator ignore?
Air resistance. For short drops of dense objects the error is small; for long falls or light objects (paper, leaves), drag dominates and actual speeds are much lower.