Calculate free fall

Solve ideal constant-acceleration free fall for height, time, and impact speed.

freeworks offlinenothing uploaded
ToolFree Fall Calculator
Input
Output
—
Put this on your own site

The frame below runs the same code as this page, in the reader's own browser. Nothing is sent to us, and nothing is sent to you.

Pick a dark background and the text and panels follow it, so the frame stays readable on a dark page.

Preview

How it works

With constant downward acceleration g, time from rest follows t = √(2h/g), final speed follows v₀ + gt, and height follows v₀t + ½gt². One of height or time is solved while the other is supplied, then impact speed is reported.

  • Standard gravity 9.80665 m/s² is used.
  • Initial velocity begins at zero and air resistance is omitted.

Worked example

Dropped from 20 metres
Starting from rest, how long it takes and how fast it lands
Input
											20
Output
												Distance metres: 20
Time seconds: 2.02
Impact speed metres per second: 19.806
Impact speed kmh: 71.301
Impact speed mph: 44.304

When to use this

Mechanics exercises predict drop time, safety demonstrations estimate ideal impact speed, and labs compare measurements with constant acceleration.

Edge cases

  • A thrown object with nonzero initial velocity needs the quadratic solution rather than the rest formula.
  • Air drag can make the ideal result too high for light, fast, or large-area objects.
  • Supplying both height and time is rejected because the solver requires one unknown.

References