Free-Fall Calculator

d = ½ g t² and v = g t. Distance and final velocity for an object falling from rest.

Inputs

Result

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General calculation reads

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How to use this calculator

  • Pick known: time or distance.
  • Enter g (9.81 Earth, 1.62 Moon).
  • Read the other + final velocity.

About this calculator

Object dropped from rest: d = ½gt², v = gt. Vacuum / no air resistance. Earth: g = 9.81 m/s². Falling from 100m: t ≈ 4.5s, v ≈ 44 m/s (98 mph). Real falls slow due to air resistance — terminal velocity for human ~55 m/s (120 mph). Galileo proved (1589, allegedly from Pisa Tower) that all objects fall at the same rate ignoring air — feathers and bowling balls.

Frequently asked

Vacuum assumption?+
Yes. Real fall through air: small/dense objects (rock) close to vacuum; large/light (feather, paper) much slower.
Terminal velocity?+
When drag balances gravity. Skydiver belly-flat: 53 m/s (190 km/h). Head-down: 90 m/s (320 km/h). Bullet: 90-100 m/s.
Why constant for all objects?+
F = mg, F = ma → a = g, independent of m. Only valid in vacuum.
What if launched horizontally?+
Vertical falls per d = ½gt². Horizontal motion is unrelated. Same vertical fall as a stationary drop.
Moon free-fall?+
g_moon = 1.62 m/s². 100m fall takes 11.1s vs. Earth's 4.5s.

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