Free fall is motion under gravity alone, with no other forces. The Toolenza calculator solves the three equations of constant acceleration — v = g · t, d = ½ g · t², v² = 2g · d — for whichever variable you don't know.

Numbers worth remembering

• g ≈ 9.81 m/s² on Earth, 1.62 on the Moon, 3.71 on Mars.
• 1-second drop = 4.9 m fallen, hitting 9.8 m/s (35 km/h, 22 mph) — already injury-territory.
• 3-second drop = 44 m fallen, hitting 29.4 m/s (106 km/h, 66 mph) — fatal.
• Terminal velocity (where drag balances gravity) for a human in skydiving position is roughly 53 m/s (~120 mph), reached after about 12 seconds of free-fall.

The drag caveat

This calculator ignores air resistance, which is fine for short drops (< 50 m). Past that, the no-drag answer overestimates impact speed badly — a real terminal-velocity skydiver hits the ground at ~120 mph, not the 3,000+ mph the formula would predict for a 6 km jump.

Where it applies

Physics homework, falling-object safety estimates, intro-to-kinematics problems, and the first-pass analysis of any "how fast does X fall" question.