Free Fall Calculator

With the free fall calculator, you can determine in just a few seconds how long it takes for an object dropped from a given height to reach the ground, and what impact velocity it will have upon arrival. Simply enter the height (in meters or feet), and the calculator instantly returns the fall time and final velocity based on fundamental physics equations.
The calculation assumes no air resistance, so the results are theoretical and indicative, but they are extremely useful for quick estimates, education, experiment planning, and engineering-level order-of-magnitude checks.

Free fall is one of the most frequently discussed basic phenomena in physics classes, engineering calculations, sports and safety contexts, and even everyday “what happens if…” questions. The purpose of this calculator is to quickly estimate, from a given drop height:

• Fall time (how long the object is in the air)

• Impact velocity (the speed at which it reaches the ground)

These two values alone already provide a strong intuitive understanding of the motion. Many people are surprised to see that even a drop from 10–20 meters results in impact within just a couple of seconds, and that velocity increases rapidly with height.
This calculator is particularly useful for:

• learning and verification (physics, mechanics),

• engineering estimates (structures, drop tests, preliminary checks),

• educational content (quick validation of examples and exercises),

• visualization and intuition building (understanding square-root relationships).

What the calculator actually computes

The calculator uses the classical ideal free fall model, which assumes that the object:

• starts from rest (initial velocity = 0),

• falls with constant gravitational acceleration (g),

• experiences no air resistance,

• experiences no buoyant force,

• is unaffected by wind, rotation, or aerodynamic lift.

The two core equations are:

• Fall time:
  t = √(2h / g)

• Impact velocity:
  v = √(2gh)

where:

• h = drop height (meters),

• g = gravitational acceleration (typically 9.80665 m/s²),

• t = time in seconds,

• v = velocity in m/s.

A key takeaway from these formulas is that time and velocity do not increase linearly with height, but according to a square-root relationship. For example, quadrupling the height only doubles the fall time and impact velocity (in the ideal model).

How to interpret the results

Fall time

The fall time tells you how long the object remains airborne. This is useful for:

• illustrating reaction times and timing,

• motion analysis in video recordings,

• sanity checks in educational exercises.

Important: if the object is thrown downward, the fall time will be shorter. If it is thrown upward and then falls back to the same level, a completely different calculation is required that includes both upward and downward motion.

Impact velocity

Impact velocity indicates the speed at which the object reaches the ground according to the ideal model. The calculator typically displays this value in multiple units:

• m/s (SI unit, standard in physics),

• km/h (more intuitive for everyday comparison),

• mph (useful in imperial/US contexts).

Velocity alone does not define “danger,” but it is a critical starting point, as many engineering and safety considerations are directly linked to speed and energy.

Why air resistance matters so much

In real-world scenarios, air resistance can significantly alter the results. The deviation from the ideal model increases with:

• larger surface area relative to mass,

• higher drag coefficient (shape),

• higher air density,

• higher velocity.

When deviations become large

• Paper sheets, feathers, light plastics: the ideal model becomes almost meaningless due to strong drag.

• Umbrellas, flat objects: air resistance dominates, resulting in much lower terminal speeds.

• Dense, compact objects (balls, metal parts): closer to ideal behavior, though at large heights drag still matters.

Terminal velocity explained

With air resistance included, falling objects eventually reach a point where velocity no longer increases significantly. This is called terminal velocity, where drag balances gravitational force.
For a human body (without a parachute, belly-to-earth position), terminal velocity is far lower than what the ideal formula would predict from hundreds of meters.
This calculator intentionally does not model terminal velocity; it focuses on the simple, educational ideal case.

Why gravity is taken as 9.81 m/s²

In everyday calculations, gravity is often rounded to 9.81 m/s² because it is easy to remember and sufficiently accurate. In reality, gravitational acceleration:

• depends on Earth’s shape,

• varies with latitude,

• changes slightly with altitude,

• is influenced by Earth’s rotation.

For everyday heights and educational purposes, these variations are negligible, making 9.81 m/s² perfectly suitable.

Example interpretations

Example 1: 1-meter drop

• time: roughly half a second,

• velocity: a few m/s (over 10 km/h).

This explains why objects dropped from hand height hit the ground almost instantly.

Example 2: 10-meter drop

• time: roughly 1–1.5 seconds,

• velocity: already several tens of km/h.

Air resistance may still be minor for dense objects, but not for light ones.

Example 3: 100-meter drop

• time: a few seconds,

• velocity: extremely high in the ideal model.

At this height, air resistance becomes increasingly important, especially for large or lightweight objects.

(These examples illustrate order of magnitude only; the calculator provides exact values for any entered height.)

Choosing the correct drop height

The drop height (h) is the vertical distance between the starting point and the impact point. Common mistakes include:

• using slope length instead of vertical difference,

• forgetting that sloped ground still requires vertical height,

• ignoring platform height relative to ground level.

In imperial contexts, height is often given in feet (ft). The calculator converts automatically using:

• 1 ft ≈ 0.3048 m

Connection to energy: why velocity matters

In free fall, gravitational potential energy is converted into kinetic energy:

• Potential energy: Eₚ = mgh

• Kinetic energy: Eₖ = ½mv²

From this relationship, the formula v = √(2gh) can be derived. This explains why:

• velocity is independent of mass in the ideal model,

• energy depends directly on mass.

Thus, two objects of different mass fall with the same velocity (ideally), but the heavier object carries more energy upon impact.

Why this is not a “danger calculator”

It is crucial to distinguish between:

• motion (time and velocity),

• impact effects (energy dissipation, force, deformation, contact time, material behavior).

Two objects with the same impact speed can cause vastly different outcomes depending on:

• mass,

• material (rigid vs elastic),

• contact area,

• impact duration (soft ground vs concrete).

Therefore, this free fall calculator is intended for motion analysis only and does not replace safety, engineering, or risk assessments.

Typical use cases

Education and learning

• checking formulas in homework,

• practicing physics exam problems,

• interpreting time-distance and time-velocity graphs.

Engineering estimates and prototyping

• order-of-magnitude checks for drop tests,

• rough comparison with sensor or IMU data (with caution),

• preliminary feasibility assessments.

Content creation and visualization

• background calculations for blog posts and videos,

• quick “what if” explanations,

• intuitive demonstrations of gravity and acceleration.

Accuracy and limitations: simple model, fast answers

This calculator is intentionally simple in order to remain:

• fast,

• easy to understand,

• stable in a browser-based environment.

Main limitations:

• no air resistance,

• no initial velocity,

• no special environments (water, dense gases),

• no non-vertical trajectories.

For high-precision results, more advanced models with aerodynamic drag and numerical methods are required.

Frequently asked questions

Do heavier objects fall faster?
In ideal free fall, no. Time and impact velocity are independent of mass. In reality, air resistance causes lighter, high-area objects to fall more slowly.

Why doesn’t fall time increase linearly with height?
Because free fall is accelerated motion: h = ½gt², leading to t = √(2h/g).

Why show velocity in multiple units?
m/s is standard in physics, km/h is intuitive for everyday comparison, and mph is useful in imperial contexts.

Can the calculator accept height in feet?
Yes. Heights in feet are converted internally to meters before calculation, and output velocities can be shown in m/s, km/h, and mph.

Important disclaimer

This calculator provides theoretical, simplified results. Real-world outcomes depend strongly on air resistance, shape, wind, initial velocity, and impact conditions. It is excellent for education and order-of-magnitude estimation, but should not be used as the sole basis for safety, engineering, or regulatory decisions.