Without air resistance, all objects fall with the same acceleration regardless of mass, as Galileo showed.
How to use the Free Fall Calculator
- Height
- Gravitational acceleration
- Want to work backwards? Type a value into Fall time and Height is calculated for you.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Rearranging the equations of motion for constant acceleration gives the time and impact speed.
Inputs explained
| Field | What to enter |
|---|---|
| Height | Units: m, cm, mm, km, in, ft … |
| Gravitational acceleration | Units: m/s², ft/s², g |
What each result means
- Fall time = sqrt(2×[Height]÷[Gravitational acceleration])
- Impact speed = sqrt(2×[Gravitational acceleration]×[Height])
Example values
How the main result changes when Height changes and everything else stays at the example values above:
| Height (m) | Fall time (s) |
|---|---|
| 10 | 1.428 |
| 15 | 1.749 |
| 20 | 2.02 |
| 25 | 2.258 |
| 30 | 2.474 |
| 40 | 2.856 |
Formula
t = √(2h ÷ g)v = √(2gh)Worked example
Inputs — Height: 20 m; Gravitational acceleration: 9.80665 m/s².
Results — Fall time = 2.02 s; Impact speed = 19.81 m/s.
Frequently asked questions
Does air resistance matter?
For heavy compact objects over short drops, little; for feathers or long falls, a lot.
What is terminal velocity?
The speed where drag equals weight, about 55 m/s for a skydiver belly-down.
What formula does the Free Fall Calculator use?
t = √(2h ÷ g).
Can I work backwards from the result?
Yes. Type the result you want into Fall time and the calculator finds the matching height.