Free Fall Calculator — Time, Velocity & Height
Calculate free-fall time, impact velocity, and drop height from any one known value, using standard gravity (9.81 m/s²) and no air resistance.
Fall time
2.02 s
Impact velocity
19.81 m/s
Drop height
20.00 m
Kinetic energy at impact
0 J
This assumes idealized free fall: no air resistance, starting from rest, using standard gravity g = 9.81 m/s². Real falling objects (especially light or large-surface-area ones) experience real air resistance, so an object's actual impact velocity will typically be somewhat lower than this idealized figure, particularly over longer falls.
About this tool
How to use it
- Pick what you know — a drop height in meters, or a fall time in seconds.
- Enter that value.
- Optionally enter a mass in kilograms to also see kinetic energy at impact.
- Press Calculate Free Fall, or just keep typing — the results update live.
Why it matters
Free fall problems come up constantly in introductory physics, but solving them by hand means picking the right one of several related equations (time from height, velocity from time, height from time) and keeping units consistent. Entering just one known value and getting every other value back removes that step entirely.
When to use it
Useful for checking physics homework, for a quick estimate of how long an object takes to hit the ground from a given height, or for understanding how kinetic energy at impact scales with height and mass.
Good to know
This assumes idealized free fall: no air resistance, starting from rest, using standard gravity g = 9.81 m/s². Real falling objects — especially light ones or those with a large surface area relative to their weight, like a sheet of paper or a leaf — experience real air resistance, so their actual impact velocity is typically lower than this idealized figure, and can be dramatically lower over a long fall (eventually reaching terminal velocity, which this calculator does not model).
Common questions
Why doesn't this account for air resistance?
Air resistance depends heavily on an object's shape, surface area, and speed, making it a genuinely different (and much more complex) calculation than idealized free fall. This tool intentionally models the simpler idealized case that's standard in introductory physics, and explicitly discloses that real-world results — especially for light or large-surface-area objects — will differ.
What value of gravity does this use?
Standard gravity, 9.81 m/s², the conventional value used in physics problems at Earth's surface. Actual local gravity varies very slightly by latitude and altitude, but not enough to matter for a typical calculation.
Why is kinetic energy optional?
Kinetic energy needs a mass, which isn't part of a basic time/height/velocity free-fall problem — it's included as an optional extra for when you also want to know the energy of impact, not because it's always relevant.
What is terminal velocity, and why isn't it included?
Terminal velocity is the maximum speed a falling object reaches once air resistance balances gravity, and it depends on the object's shape, mass, and the density of the air — factors this idealized free-fall calculator doesn't model. For very long falls or light objects, the real answer would plateau well below what this calculator reports.