Free Fall Calculator
Fall time and impact speed from drop height in meters or feet.
What it does
Free fall drops from rest under gravity alone. Height sets both the time down and the speed at landing through two square root laws, which is why falling twice as far takes far less than twice as long.
The tool above takes the drop height in meters or feet. It returns fall seconds, impact speed, and road units (km/h or mph) for a feel of the number.
The default 10 m drop falls 1.43 s and lands at 14 m/s, about 50.4 km/h. The imperial mirror of 32.8 ft reads the same 1.43 s at 45.9 ft/s (31.3 mph).
Gravity here is the NIST standard 9.80665 m/s² with NASA drop test references showing the same roots. Air resistance is excluded, so feathers and high drops fall slower in real air than this vacuum page.
How to use
- Pick meters or feet for the height.
- Enter the vertical drop from rest.
- Read fall time first for the stopwatch number.
- Read impact speed for the landing.
- Treat tall drops as upper bounds, since drag bites hardest there.
Formula
- h
- Vertical drop from rest in meters.
- g
- Standard gravity 9.80665 m/s².
- roots
- Square roots giving the sublinear growth.
Feet convert to meters first (x 0.3048), then run the same metric roots, so both systems agree. Zero initial velocity assumed; thrown objects add their own terms.
Worked example
Example: 10 m drop
Metric default: 10 m, from rest.
- Time: root(2 x 10 / 9.80665) = root(2.0394) = 1.43 s.
- Impact: root(2 x 9.80665 x 10) = root(196.13) = 14 m/s.
- Road: 14 x 3.6 = 50.4 km/h.
- Check: 14 / 1.43 = 9.79, near g as kinematics requires.
- Tool shows 1.43 s, 14 m/s, 50.4 km/h.
Reference table
| Height | Time | Impact |
|---|---|---|
| 1 m | 0.45 s | 4.4 m/s |
| 10 m | 1.43 s | 14 m/s |
| 100 m | 4.52 s | 44.3 m/s |
Limits
- Vacuum only; drag slows real falls, badly for light shapes.
- From rest; thrown starts need extra terms.
- Constant g assumed over the drop.
- Landing forces need stopping distance beyond speed.
Common mistakes
- Scaling time linearly with height.
- Mixing feet with metric g without converting.
- Reading impact speed as survivable from any height.
- Ignoring drag on high or fluffy drops.
- Forgetting the square root in both formulas.
Try it yourself
Quick checks. Answers sit tucked under each question.
5 m drop time?
root(10/9.80665) = root(1.0197) = 1.01 s.
1 m impact?
root(19.61) = 4.4 m/s.
32.8 ft in metric?
32.8 x 0.3048 = 10 m, so 1.43 s.
Questions
How long to fall 10 m?
1.43 s in vacuum, landing at 14 m/s (50.4 km/h).
Why not double time for double height?
Roots grow sublinearly: double height multiplies time by root 2 (1.41x).
What is g?
Standard gravity 9.80665 m/s², the NIST reference value used here.
Does mass matter?
Not in vacuum; all masses fall together. Air makes mass and shape matter.
How fast is terminal velocity?
Where drag equals weight: near 55 m/s belly down for people, far below vacuum numbers from height.
Can I use this for projectiles?
Only the vertical drop part. Horizontal motion continues separately.