Free Fall Calculator
Fall time and impact speed from a drop height, or distance and speed after a given time, with optional initial velocity and gravity, plus a height-vs-time table.
Free Fall Calculator: with the default inputs, speed at the end of the fall is 14.005 m/s.
Not used in the fall-time mode.
Not used in the drop-height mode.
- Solved for
- time = 1.428 s, impact speed = 14.005 m/s
- Fall time
- 1.428 s
- Distance fallen
- 10 m
- Average speed during the fall
- 7.002 m/s
- Kinetic energy per kilogram
- 98.07 J½v² — multiply by the mass for the impact energy.
Assumptions
- No air resistance — vacuum kinematics.
- Uniform gravity over the height of the fall.
- Downward is positive for the initial velocity.
| Height(m) | Time(s) | Impact speed(m/s) | km/h |
|---|---|---|---|
| 1 m | 0.452 s | 4.43 m/s | 15.9 |
| 2 m | 0.639 s | 6.26 m/s | 22.5 |
| 5 m | 1.01 s | 9.9 m/s | 35.7 |
| 10 m | 1.428 s | 14 m/s | 50.4 |
| 20 m | 2.02 s | 19.81 m/s | 71.3 |
| 50 m | 3.193 s | 31.32 m/s | 112.7 |
| 100 m | 4.516 s | 44.29 m/s | 159.4 |
| 200 m | 6.387 s | 62.63 m/s | 225.5 |
| 500 m | 10.098 s | 99.03 m/s | 356.5 |
| 1,000 m | 14.281 s | 140.05 m/s | 504.2 |
Vacuum values. For a human body, air resistance caps the speed near 200 km/h no matter the height.
How this is worked out
The formula
h = v₀ t + ½ g t² v = v₀ + g t v² = v₀² + 2 g h Dropped from rest (v₀ = 0): t = √(2h ÷ g) v = √(2gh) = g t h = distance fallen (m), t = time (s), v = speed (m/s) g = 9.80665 m/s² (standard gravity)
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- What do you know?
- Choose one of 2 options.Drop height → fall time & impact speed · Fall time → distance fallen & speed
- Drop height
- Not used in the fall-time mode.in m · 0 or more · defaults to 10
- Fall time
- Not used in the drop-height mode.in s, ms, min · 0 or more · defaults to 2
- Initial velocity(under More options)
- Positive = thrown downward, negative = thrown upward, 0 = dropped.in m/s · defaults to 0
- Gravity(under More options)
- Earth 9.80665 (standard), Moon 1.62, Mars 3.71, Jupiter 24.79.from 0.01 to 1000 · defaults to 9.80665
What you get back
- Speed at the end of the fallmain answer
- Solved for
- Fall time
- Distance fallen
- Average speed during the fall
- Kinetic energy per kilogram
- ½v² — multiply by the mass for the impact energy.
What this assumes
- No air resistance — vacuum kinematics.
- Uniform gravity over the height of the fall.
- Downward is positive for the initial velocity.
About this calculator
Drop something and it accelerates downward at g — 9.81 m/s² on Earth — gaining 9.81 m/s of speed every second regardless of its mass. This calculator turns that constant acceleration into the numbers you actually want: how long the fall takes and how fast the object is going when it lands, or, given a time, how far it has fallen. Open More options to throw the object downward or upward first, or to change g for another planet.
The two shapes of free fall
Speed grows linearly with time (v = gt), but distance grows with the square (h = ½gt²). So the first second of a fall covers 4.9 m, the second second covers 14.7 m more, and the third another 24.5 m. Doubling the height does not double the fall time — it multiplies it by √2. The table under the results lays this out from 1 m to 1 km.
Reading the results
- Speed at the end is what matters for impact: from 10 m (a three-storey window) it is 14 m/s, 50 km/h — a serious car crash. Switch the unit to km/h or mph for intuition.
- Average speed during the fall is half the final speed when dropped from rest, which is why h = ½gt² has the ½ in it.
- Kinetic energy per kilogram is ½v²; multiply by the mass for the energy that must be absorbed on landing.
- A negative initial velocity means thrown upward: the time includes the rise and the return, and the impact speed is the same as if thrown downward at the same speed.
Common mistakes
- Using g = 10 m/s² and expecting textbook answers to match to three figures; the standard value is 9.80665.
- Mixing units: heights in feet with g in m/s². The calculator converts, but hand calculations must too (g = 32.17 ft/s²).
- Forgetting air. See below.
Where the model breaks
Everything here is in vacuum. Air drag grows with speed squared and eventually balances gravity at terminal velocity: about 55 m/s (200 km/h) for a belly-down skydiver, 9 m/s for a raindrop, under 1 m/s for a feather. For dense objects over short drops — a wrench from a ladder, a phone from a balcony — the vacuum numbers are within a few percent. For anything light, or any fall over a few seconds, treat them as an upper limit.
Frequently asked questions
▸How do I calculate free fall time from height?
t = √(2h ÷ g). From 10 m: √(20 ÷ 9.80665) = 1.43 s. Ignore air resistance and start from rest.
▸What is the speed of an object after falling a certain distance?
v = √(2gh). From 10 m that is √(2 × 9.80665 × 10) = 14.0 m/s, or about 50 km/h (31 mph).
▸Does a heavier object fall faster?
Not in vacuum — Galileo's result, confirmed by the Apollo 15 hammer-and-feather drop. In air, heavier objects of the same shape reach a higher terminal velocity because drag matters less relative to their weight.
▸How far does an object fall in one second?
4.9 m from rest (½ × 9.81 × 1²). In two seconds 19.6 m, in three 44.1 m — the distance grows with the square of the time.
▸What is terminal velocity?
The steady speed at which air drag equals weight, so acceleration stops. It is about 55 m/s for a skydiver spread out, over 80 m/s head-down, and much less for light or fluffy objects. This calculator ignores it.
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