Free Fall Calculator
Compute free-fall height, fall time, initial speed, and final speed with ease. Enter any two values and get the other two instantly. The tool is free, delivers instant results, and is friendly to local number formats.
Number format
Choose how numeric results are displayed. The selected decimal separator (dot or comma) will also be used when parsing input numbers.
Free Fall Calculator — quick guide
This calculator lets you enter any two of the four main values — height (h), fall time (t), initial speed (v₀), and final speed (v) — and it will instantly work out the other two. Here, speed is always treated as positive in the downward direction, which matches everyday intuition.
What is “free fall” in this tool?
We assume motion under constant gravity with no air resistance. Gravity is set by default to 9.81 m/s², but you can change it if you want to explore conditions on the Moon or other planets.
- Height (h): how far the object falls, in meters.
- Fall time (t): how long it takes to reach the ground or a given point, in seconds.
- Initial speed (v₀): the starting downward speed at release, in meters per second. If released from rest, use v₀ = 0.
- Final speed (v): the downward speed at the end of the fall or at impact.
Available input pairs
The calculator works with these combinations:
| Given (two) | Calculator finds |
|---|---|
| Height + Initial speed | Fall time, Final speed |
| Height + Fall time | Initial speed, Final speed |
| Initial speed + Fall time | Final speed, Height |
| Initial speed + Final speed | Fall time, Height |
| Fall time + Final speed | Initial speed, Height |
Worked examples
Example A — Drop from rest
Given: h = 100 m, v₀ = 0
Find: t, v
t = √(2h / g) = √(200 / 9.81) ≈ 4.52 s v = g × t ≈ 9.81 × 4.52 ≈ 44.3 m/s
Example B — With initial downward speed
Given: h = 80 m, v₀ = 6 m/s
Find: t, v
Equation: h = v₀ t + ½ g t² → 80 = 6t + 4.905t² → t ≈ 4.09 s v = v₀ + g t ≈ 6 + 9.81×4.09 ≈ 46.1 m/s
Quick reference (drop from rest, v₀ = 0)
Handy numbers for Earth gravity (g = 9.81 m/s²). Speeds are positive downward.
| Height h (m) | Fall time t (s) | Final speed v (m/s) |
|---|---|---|
| 5 | 1.01 | 9.9 |
| 10 | 1.43 | 14.0 |
| 20 | 2.02 | 19.8 |
| 50 | 3.19 | 31.3 |
| 100 | 4.52 | 44.3 |
Tips for input and units
- Units: Use meters (m), seconds (s), and meters per second (m/s).
- Inputs: Speeds are always positive downward. If the object starts from rest, enter v₀ = 0.
- Gravity: Default is 9.81 m/s². You can adjust for different conditions.
FAQ
Can I change the value of gravity?
Yes, set g to any positive value. For example, the Moon uses about 1.62 m/s².
Does this include air resistance?
No, it's an idealized model. For small heights and ordinary speeds it's a good estimate, but real objects fall slower due to drag.
Why does the formula t = √(2h/g) not always match?
That shortcut works only if initial speed is zero. With non-zero initial speed, you need the full motion equations to solve correctly.