Free Fall Calculator
How long something dropped from a height takes to fall and how fast it lands, or how far it falls in a time, with no air resistance.
Result
Time to fall: 2.493 s
No air resistance. A real object falls more slowly and levels off at its terminal speed.
- Speed at the bottom
- 54.69 mph (80.22 ft/s)
- Distance fallen
- 100 ft
- Average speed
- 27.35 mph (40.11 ft/s)
https://calcgallery.com/physics/free-fall-calculator/
Results come from the published equations applied to the values you enter. They are not electrical design, conductor sizing, laboratory safety or medical guidance. Weather indices describe a standard person in standard conditions and are not a forecast. Where codes apply, local rules vary and must be checked. Read the full disclaimer
How to use the Free Fall Calculator
- Choose what you know, the height of the drop, how long it falls, or the speed it reaches.
- Enter it. The object is taken as let go from rest.
- Read the fall time, landing speed and distance. Change gravity under more options for a textbook’s 9.8 m/s² or another world.
The formulas
from a height: t = √(2h ÷ g), v = g × tfrom a time: h = ½ × g × t², v = g × tfrom a speed: t = v ÷ g, h = v² ÷ 2gThe average speed on the way down is half the landing speed, because the speed grows steadily from zero.
Limits
The object starts at rest and nothing but gravity acts on it. For a throw upwards, downwards or sideways, use the projectile motion calculator. Air resistance, terminal velocity and the fall-off of gravity with altitude are left out, and the page says nothing about what a fall would do to a person or an object.
With your numbers
- t = √(2h ÷ g) = √(2 × 100 ft ÷ 32.174 ft/s²) = 2.49323 s
- v = g × t = 80.2173 ft/s
Quick reference
No air resistance. A real object falls more slowly and levels off at its terminal speed.
| Example | Result |
|---|---|
| Dropped 100 ft | Time to fall: 2.493 s |
| Dropped 20 m | Time to fall: 2.02 s |
| Dropped 1 m | Time to fall: 0.4516 s |
| Falling for 1 s | Distance fallen: 4.903 m |
| Falling for 3 s | Distance fallen: 44.13 m |
| Height to reach 30 m/s | Distance fallen: 45.89 m |
| Height to reach 60 mph | Distance fallen: 120.3 ft |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
1 source
SI Brochure, 9th ed. (BIPM, 2019), Appendix 1, 3rd CGPM (1901), Declaration on the unit of mass and on the definition of weight, p. 154: "The value adopted in the International Service of Weights and Measures for the standard acceleration due to gravity is 980.665 cm/s2", https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf
Used for
- Standard acceleration of gravity, gₙ, a conventional value fixed by definition. Real gravity differs slightly from place to place, and on other worlds far more, so pages let you change it.
Common questions about the Free Fall Calculator
- How long does it take to fall from a height?
- Without air resistance, t = √(2h ÷ g). From 20 m that is √(40 ÷ 9.80665) ≈ 2.02 s, and from 100 ft about 2.49 s. The time grows with the square root of the height, so four times as high takes only twice as long.
- How fast does a falling object hit the ground?
- Its speed is v = gt, or v = √(2gh) from the height. A 20 m drop lands at about 19.8 m/s, roughly 71 km/h, and a 100 ft drop at about 80 ft/s, some 55 mph. Mass does not appear: without air, a hammer and a feather land together.
- How far does something fall in a given time?
- h = ½gt². In the first second it falls about 4.9 m, and after 3 s it has fallen about 44 m and is moving at about 29 m/s. Each second it falls further than the last, which is what the spacing in the diagram shows.
- Why is the real answer different?
- Air pushes back harder the faster something moves, until the drag balances the weight and the speed stops growing. A falling skydiver soon stops speeding up, and a small, light object sooner still. For short drops of dense objects the difference is small; for long falls the page overstates the speed.
- What value of g does the page use?
- Standard gravity, 9.80665 m/s², a conventional value fixed in 1901. Real gravity at the Earth’s surface is a little different from place to place, and textbooks often round it to 9.8 or 9.81. Enter any value under more options, including another planet’s.