Free Fall Calculator

Compute drop height, fall time, and impact velocity

Analyze free fall motion with gravity, height, time, and velocity. Supports bidirectional LRU solving and multiple unit systems.

Last updated: December 19, 2025

CreatorFrank Zhao

Free Fall Parameters

Gravitational Acceleration (g)

More info

m/s²

Initial Velocity (v₀)

More info

m/s

Drop Height (h)

More info

Fall Duration (t)

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sec

Impact Velocity (v)

More info

m/s

Motion Summary

Average Speed

More info

m/s

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Introduction / overview

The Free Fall Calculator helps you estimate how fast an object is moving and how far it travels when gravity is the only acceleration. It’s the classic “dropped apple” model: clean, simple, and great for quick checks.

✅ Best for: classroom problems, quick engineering sanity checks, and “how long / how fast” estimates when air resistance is small.

What you can solve for

Fall time (how long it takes)
Drop height / distance traveled
Impact (final) velocity

Who uses it

Students learning kinematics
Builders / DIYers checking drop times and speeds
Anyone comparing “ideal” vs “real” falling motion

If you want a more realistic model where the object stops accelerating and approaches a terminal speed, use our Free Fall with Air Resistance Calculator.

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Accuracy note:

This calculator uses constant gravitational acceleration $g$ (you can change it). That’s a great approximation for many everyday heights.

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How to use / quick start guide

The calculator is “bidirectional”: enter any two of the kinematics fields (plus gravity) and it solves the others. Most people start with “height + initial velocity” or “time + initial velocity.”

Pick your gravity

For Earth, a common default is $g \approx 9.80665\ \text{m/s}^2$ . For another planet, change $g$ to match your scenario.

Decide the initial velocity

Dropped from rest? Use $v_0 = 0$ . Thrown downward? Use a positive $v_0$ . Thrown upward? Use a negative $v_0$ (the calculator can handle it).

Enter two known fields

Examples: (a) enter height and time, or (b) enter height and impact velocity. The calculator will solve the remaining fields.

Read the results (and sanity-check)

You’ll get final velocity, fall time, and distance. A quick check: if $v_0 = 0$ , then velocity should grow linearly with time: $v \propto t$ .

Worked example (copy this): drop for 8 seconds

Assume $v_0 = 0$ and $g = 9.80665\ \text{m/s}^2$ .

Final speed

v = v_0 + gt = 0 + (9.80665)(8) = 78.45\ \text{m/s}

Distance fallen

s = v_0 t + \frac{1}{2}gt^2 = 0 + \frac{1}{2}(9.80665)(8^2) = 313.8\ \text{m}

Interpretation: at 8 seconds, the object is moving about $78.45\ \text{m/s}$ and has fallen about $313.8\ \text{m}$ (in the ideal no-drag world).

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Real-world examples / use cases

Here are practical scenarios that match how people actually use this tool. Each example shows concrete inputs and the result you can apply.

Example 1: Dropping a phone from a balcony

Background: You want a rough idea of impact speed from a $h = 12\ \text{m}$ drop. Assume it starts from rest $v_0 = 0$ .

Time to fall

t = \sqrt{\frac{2h}{g}} = \sqrt{\frac{2(12)}{9.80665}} \approx 1.56\ \text{s}

Impact speed

v = gt \approx (9.80665)(1.56) \approx 15.3\ \text{m/s}

How to use it: treat this as an upper-bound estimate; real impact speed may be slightly lower if drag matters.

Example 2: Timing a short lab drop

Background: In a simple physics lab, you measure a fall time of $t = 0.70\ \text{s}$ from rest. What height does that correspond to?

h = \frac{1}{2}gt^2 = \frac{1}{2}(9.80665)(0.70^2) \approx 2.40\ \text{m}

How to use it: compare to your measured setup height. If it’s way off, your reaction time or timing method is likely the culprit.

Example 3: Estimating speed from a known height

Background: An object falls through $h = 45\ \text{m}$ starting from rest. What’s the speed right before it hits?

v = \sqrt{2gh} = \sqrt{2(9.80665)(45)} \approx 29.7\ \text{m/s}

How to use it: if you’re doing a safety check, treat this as the “no-drag” baseline. For real-world planning at higher speeds, compare with the air-resistance version.

Example 4: Free fall is also “upward” motion

Background: You throw a ball upward with $v_0 = -12\ \text{m/s}$ . How long until its velocity becomes zero at the top?

0 = v_0 + gt \Rightarrow t = \frac{-v_0}{g} = \frac{12}{9.80665} \approx 1.22\ \text{s}

How to use it: negative $v_0$ simply means “upward” under this sign convention. If you’re also interested in horizontal motion, try our Projectile Motion Calculator.

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Common scenarios / when to use

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Homework & exams

Fast kinematics checks for time, distance, and velocity.

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DIY & safety intuition

Estimate how quickly something hits the ground from a height.

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Other planets (what-if)

Change g and explore different gravitational environments.

⚠️ Not ideal when: the object reaches high speed in air (skydiving, long drops) — drag can dominate. In that case, use the air-resistance calculator.

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Tips & best practices

Use consistent units

The calculator handles conversions, but your intuition is easier if you stick to one system (e.g., meters + seconds).

Remember: height does not depend on mass

In the ideal model, mass cancels out. Differences in real life mostly come from air resistance and shape.

Treat results as a baseline

If you care about precision at high speed, compare with the drag-inclusive model (terminal velocity matters).

Watch for sign conventions

If you enter a negative $v_0$ (thrown upward), some intermediate results can look “unexpected” until the object turns around.

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Calculation method / formula explanation

The calculator uses the standard constant-acceleration kinematics equations. Here we treat downward motion as positive, with constant acceleration $g$ .

Core equations

v = v_0 + gt

h = v_0 t + \frac{1}{2}gt^2

v^2 = v_0^2 + 2gh

Variable meanings

$h$ : vertical distance (drop height), in meters/feet
$t$ : time of fall
$v_0$ : initial velocity (can be negative for upward throw)
$v$ : velocity at time $t$ (often the impact velocity)
$g$ : acceleration due to gravity

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Common shortcut: If an object is dropped from rest ( $v_0=0$ ), you can jump straight to $h = \frac{1}{2}gt^2$ and $v = \sqrt{2gh}$ .

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Related concepts / background info

What is “free fall” (definition)?

In physics, an object is in free fall when gravity is the only force acting on it. That means there’s only one acceleration: $g$ . Real objects in air are also pushed by drag, which is why the “ideal” model becomes less accurate at high speeds.

Free fall speed (why it grows linearly)

With constant acceleration, velocity changes by the same amount each second. That’s exactly what $v=v_0+gt$ says.

Time (s)	Speed from rest (m/s)	Time (s)	Speed from rest (m/s)
1	9.8	4	39.2
2	19.6	5	49.0
3	29.4	6	58.8

Note: the table uses $g \approx 9.8\ \text{m/s}^2$ for easy mental math.

Why doesn’t mass matter (in the ideal model)?

Gravity pulls harder on heavier objects, but it also takes more force to accelerate them. Those effects cancel, so ideal free fall depends on $g$ — not mass. The “feather vs brick” difference you see in real life is mostly air resistance.

How to estimate gravity on another planet

If you know a planet’s mass $M$ and radius $r$ , the surface gravitational acceleration is approximately:

g = \frac{GM}{r^2}

Here $G$ is the universal gravitational constant.

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Highest free fall in history (and why “ideal” is different)

A “pure” free fall is only possible in a vacuum. On Earth, even skydivers experience strong drag. Still, high-altitude jumps from the stratosphere are about as close as humans get to the textbook idea.

For example, in the 2010s there were famous near-space balloon jumps (such as Felix Baumgartner and Alan Eustace) where the jumper fell for many minutes. In those situations, the “no air resistance” model becomes a dramatic overestimate of speed — which is exactly why terminal velocity is a key concept.

If you want a model that naturally “levels off” in speed, use the Free Fall with Air Resistance Calculator.

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Frequently Asked Questions

What is free fall speed?

In the ideal model (no drag), speed increases linearly with time: $v = v_0 + gt$ . If dropped from rest, that becomes $v = gt$ .

Tip: if you need “real” speeds in air (terminal velocity), use the air-resistance version.

Why is the weight of a free-falling body “zero”?

It isn’t. Weight is still $W = mg$ . What can become “zero” is the apparent weight (the normal force you feel) when you and your scale are both accelerating together.

What’s the difference between free fall and weightlessness?

Free fall describes the motion (gravity is the only significant force). Weightlessness describes what you feel (no support force). You can feel weightless during free fall even though gravity is still acting.

How do I find free fall acceleration on another planet?

Use $g = \frac{GM}{r^2}$ where $M$ is the planet mass and $r$ is its radius. Then plug that $g$ into this calculator.

Tip: make sure $r$ is in meters to keep units consistent.

Does this calculator include air resistance or terminal velocity?

No — this is the ideal constant-acceleration model. For drag and terminal velocity, use the Free Fall with Air Resistance Calculator.

Why do I see warnings or “no physical solution”?

Some combinations of inputs cannot happen in ideal free fall. For instance, if you provide a very small impact speed for a very large height, it violates $v^2 = v_0^2 + 2gh$ .

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Limitations / disclaimers

This calculator is for educational and estimation purposes. It does not replace professional safety, engineering, or medical advice.

Main limitations

Assumes constant $g$ and straight-line vertical motion.
Neglects drag, wind, lift, and rotation.
For very large heights, changes in air density and $g$ can matter.

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