β¬οΈ Free Fall Calculator
Calculate time of fall and final velocity from drop height.
How to Use This Calculator
This calculator solves free-fall problems for an object dropped from rest. Enter the drop height and the gravitational acceleration, and it returns the fall time and impact velocity.
Enter the drop height in meters, measured from the release point to the ground.
Check the value of g. It defaults to 9.81 m/s^2 for Earth. Change it to 1.62 for the Moon or 3.71 for Mars.
Click Calculate. You get the time to fall and the velocity at impact.
The calculation assumes the object starts from rest and air resistance is negligible.
The Free-Fall Formulas
Free fall is motion under gravity alone, with no other forces. Galileo's great insight was that all objects accelerate identically, so mass cancels out of every equation. These formulas come from the kinematics equations with initial velocity zero and acceleration g. Time grows with the square root of height: falling four times farther takes only twice as long.
The velocity formula v = sqrt(2gh) is really an energy statement in disguise. It says the kinetic energy at impact (1/2 x mv^2) equals the gravitational potential energy lost (mgh). The mass appears on both sides and cancels, which is the mathematical reason heavy and light objects fall together.
Worked Example
Where This Comes Up
Free-fall math appears in physics homework constantly, but it also answers everyday questions. How long does a dropped phone take to hit the floor from a second-story balcony? About 1.4 seconds from 10 m, hitting at 14 m/s. Stunt coordinators, packaging engineers designing drop tests, and geologists timing stones down mine shafts all use these same three formulas.
Remember the square-root trap: doubling the height does not double the fall time, it multiplies it by about 1.41. And air resistance matters more than beginners expect for light, flat objects. A sheet of paper dropped from 2 m takes far longer than the formula predicts, while a stone matches it closely. Use the calculator for dense objects and short drops, and treat results for feathers and parachutes with suspicion.
Frequently Asked Questions
Does a heavier object fall faster?
No. In the absence of air resistance, all objects accelerate at the same rate g, regardless of mass. A bowling ball and a marble dropped together hit the ground together. Air resistance is the only reason a feather falls slower.
What value should I use for g?
Use 9.81 m/s^2 near Earth's surface. The calculator lets you change it, which is handy for the Moon (1.62 m/s^2) or Mars (3.71 m/s^2).
What formulas does this calculator use?
For a drop from rest: fall time t = sqrt(2h/g), impact velocity v = sqrt(2gh), and equivalently v = g x t. All three describe the same motion.
Why is air resistance ignored?
Including drag needs the object's shape, size, and drag coefficient, and the math gets complicated fast. For dense objects falling short distances, ignoring air gives answers within a few percent of reality.
How do I find the height if I know the fall time?
Rearrange the time formula: h = 1/2 x g x t^2. Time a stone falling down a well for 3 seconds and the well is about 0.5 x 9.81 x 9 = 44.1 m deep.