Free Fall Calculator
Solve any free fall problem from the value you know. Enter a fall time, a drop height, or a target impact speed, add an optional initial (thrown) speed, pick the gravity of Earth, the Moon, Mars or another body, and get the fall time, distance fallen and final velocity with the full working shown.
Formula
Worked example
Drop an object from rest for 3 s with g = 9.81 m/s²: distance d = ½ × 9.81 × 3² = 44.1 m, and final velocity v = 9.81 × 3 = 29.4 m/s, about 106 km/h. On the Moon (g = 1.62 m/s²) the same 3 s gives only 7.3 m and 4.9 m/s.
What free fall means
Free fall describes the motion of an object acted on by gravity alone, with no air resistance, lift, or thrust to interfere. Near a planet’s surface every freely falling object accelerates downward at the same constant rate, g, regardless of its mass, so a feather and a hammer dropped in a vacuum land together. On Earth that rate is about 9.81 metres per second squared. Because the acceleration is constant, the kinematic equations simplify neatly: the distance fallen is d = v0t + ½gt² and the speed gained is v = v0 + gt, where v0 is any downward speed the object already had at release. Drop something from rest and v0 is zero, which recovers the familiar d = ½gt² and v = gt.
Solving from time, height or impact speed
This calculator works in three directions. Give it a fall time and it returns the distance and impact velocity directly. Give it a drop height and it rearranges d = ½gt² to t = √(2d/g) to find the fall time first, then the impact speed, or it solves the full quadratic when the object was thrown downward. Give it a target impact velocity and it works backward through v = gt to the time and height. You can also pick the gravity of the body you are on, the Moon, Mars, Jupiter or a custom value, since the same drop plays out very differently where g is weaker or stronger.
Initial velocity and the limits of the model
If the object is thrown straight down rather than released gently, enter its initial speed in the advanced field. The fall then covers more ground in the same time and reaches a higher impact speed, following d = v0t + ½gt² and v = v0 + gt. Remember that these idealized results overstate real speeds for light or large objects: air resistance grows with speed until it cancels gravity, capping the fall at a terminal velocity that no amount of extra height will exceed. A human in a belly-to-earth position tops out near 53 m/s (about 190 km/h), so the equations here are accurate for short drops and dense objects but optimistic for long ones.
Free fall from rest by body (no air resistance)
| Body | Gravity (m/s²) | Distance after 3 s (m) | Speed after 3 s (m/s) |
|---|---|---|---|
| Earth | 9.81 | 44.1 | 29.4 |
| Moon | 1.62 | 7.3 | 4.9 |
| Mars | 3.72 | 16.7 | 11.2 |
| Jupiter | 24.79 | 111.6 | 74.4 |
| Sun | 274 | 1233 | 822 |
Distance and speed after a 3 second drop, showing how surface gravity changes the result.
Frequently asked questions
What is the formula for free fall?
The distance fallen is d = v0t + ½gt² and the final velocity is v = v0 + gt, where g is the acceleration due to gravity (9.81 m/s² on Earth), t is the time, and v0 is any downward speed at release. From rest (v0 = 0) these reduce to d = ½gt² and v = gt, and the time from a drop height is t = √(2d/g).
Does a heavier object fall faster?
No. In free fall with no air resistance, every object accelerates at the same rate g regardless of mass, so they fall at identical speeds. Heavier objects only seem to fall faster in everyday life because air resistance affects light, large objects more than dense, compact ones.
How do I calculate free fall on the Moon or Mars?
Use the same equations but swap in that body’s surface gravity: about 1.62 m/s² on the Moon, 3.72 m/s² on Mars and 24.79 m/s² on Jupiter, versus 9.81 m/s² on Earth. Select the body in the calculator and it substitutes the right g, so a 3 second drop covers 44 m on Earth but only about 7 m on the Moon.
Why does the calculator ignore air resistance?
The equations assume gravity is the only force acting. Real falls slow as air drag builds, eventually reaching a terminal velocity (about 53 m/s for a skydiver). These formulas are accurate for short drops and dense objects but overstate the speed of long falls through air.