Free Fall Calculator
Drop something from rest and this finds the fall time, the drop height, and the speed it hits the ground.
Enter a drop height or a fall time — leave the other blank — for an object dropped from rest. The calculator fills in the missing one and gives the speed at impact. Air resistance is ignored, and gravity is fixed at 9.81 m/s².
Drop height
45m
Fall time
3.029s
Impact velocity
29.714m/s
How it works
When you let go of something from rest, gravity does all the work. The distance it falls grows with the square of time — h equals one-half g times t squared — so the object covers far more ground in its second second than its first. Rearranging that gives the fall time from a height, t = √(2h/g).
Impact speed comes from the same physics. Every meter of fall adds kinetic energy, and the speed at the bottom works out to v = √(2gh). Drop something from 45 meters and it lands after about 3.03 seconds, hitting the ground at roughly 29.7 m/s — around 107 km/h.
Fill in either the height or the time and leave the other blank; the calculator solves for it and reports the impact velocity too. Like the textbook version, it assumes no air resistance, so a real feather or sheet of paper won't match — but a dense object over a short drop comes very close.
Frequently asked questions
Does mass affect how fast something falls?
Not in free fall. Ignoring air resistance, a bowling ball and a marble dropped together hit the ground at the same moment, because gravity accelerates everything at the same 9.81 m/s². Mass only starts to matter once air drag enters the picture.
Why doesn't my real-world drop match the numbers?
Air resistance. This calculator assumes a vacuum, so light or spread-out objects — a leaf, a crumpled receipt — fall slower than predicted. Compact, heavy objects over modest heights track the formula closely.
What if the object is thrown down instead of dropped?
Then it isn't starting from rest, so these formulas don't apply directly — you'd add the initial downward speed. This tool is built for the pure drop-from-rest case, which is the most common textbook setup.