Introduction
Free fall happens when an object drops under the pull of gravity alone, with no other forces acting on it. Whether you're solving a physics homework problem or just curious how long it takes a ball to hit the ground, our Free Fall Calculator gives you quick and accurate answers. Enter a height, pick a planet, and instantly find the fall time, final velocity, kinetic energy, and more — all with step-by-step solutions and clear graphs.
This tool covers four key modes: simple free fall from rest, free fall with an initial velocity (like throwing a ball upward), an energy calculator that shows potential and kinetic energy, and an advanced mode that factors in air resistance and terminal velocity. You can switch between units such as meters, feet, kilometers, and miles, and even compare how gravity works on Earth, the Moon, Mars, Jupiter, and other celestial bodies. Each calculation displays the formulas used and walks you through every step so you can learn the physics behind the numbers.
How to use our Free Fall Calculator
Enter details about a falling object to find out how long it takes to hit the ground, how fast it will be going, and how much energy it will have at impact. This calculator has four modes: Simple Free Fall, With Initial Velocity, Energy Calculator, and With Air Resistance.
Select Celestial Body: Pick the planet or moon where the object is falling. You can choose Earth, Moon, Mars, Jupiter, Venus, Saturn, or set a custom gravity value. This changes the gravitational acceleration used in the calculation. To explore how gravity works between two masses in more detail, try our Gravitational Force Calculator.
Initial Height: Enter how high the object starts before it begins to fall. You can type a number or use the slider. Choose your preferred unit from meters, feet, kilometers, miles, inches, or centimeters.
Time (optional): If you want to know the object's position and speed at a specific moment during the fall, enter a time value here. Leave it blank to calculate the full fall from top to bottom. You can use seconds, milliseconds, or minutes.
Mass: Enter the mass of the falling object. This is used to calculate kinetic energy, potential energy, and impact force. Choose from kilograms, grams, pounds, or ounces.
Gravity: This field is set automatically when you pick a celestial body, but you can also type in any value you want. Units available are m/s², ft/s², or g-force. For more on how g-forces affect objects and people, see our G Force Calculator.
Initial Velocity (With Initial Velocity tab): Enter the speed of the object at the start of the fall. Use a positive number if the object is thrown upward and a negative number if it is thrown downward. Choose from m/s, km/h, mph, or ft/s.
Velocity (Energy Calculator tab): Enter the current speed of the object in meters per second to calculate its kinetic energy at that moment, along with its potential energy based on the height you provide.
Drag Coefficient (Air Resistance tab): Enter the drag coefficient of the falling object. This number depends on the object's shape. A typical value for a person falling spread-eagle is about 0.7.
Cross-Section Area (Air Resistance tab): Enter the area of the object that faces the oncoming air, measured in square meters. For a skydiver in a spread position, this is roughly 0.7 m².
Quick Examples: Click one of the preset scenarios — a penny dropped from the Empire State Building, Felix Baumgartner's record-breaking skydive, or Galileo's famous Leaning Tower of Pisa experiment — to instantly load real-world values into the calculator.
Understanding Free Fall
Free fall is the motion of an object falling only under the influence of gravity, with no other forces acting on it. When you drop a ball, jump off a diving board, or watch a raindrop fall from the sky, you are seeing free fall in action. During free fall, every object speeds up at the same steady rate regardless of its mass. On Earth, that rate is about 9.8 meters per second squared (9.8 m/s²), which means an object's speed increases by roughly 9.8 m/s for every second it falls. This constant increase in speed is a form of acceleration, which you can explore further with our Acceleration Calculator.
Key Free Fall Formulas
Three main equations describe free fall when an object starts from rest:
- Time to fall: t = √(2h / g) — This tells you how long it takes an object to hit the ground when dropped from height h.
- Final velocity: v = g × t — This gives the speed of the object right before it hits the ground.
- Distance fallen: d = ½ × g × t² — This tells you how far the object has fallen after a certain amount of time. You can use our Displacement Calculator to work with more complex distance and displacement problems.
In these formulas, g stands for gravitational acceleration, t is time, h is height, and v is velocity. These equations assume there is no air resistance slowing the object down.
Free Fall with Initial Velocity
Sometimes an object isn't simply dropped — it's thrown upward or downward. When you throw a ball straight up, it slows down, stops for an instant at its highest point, and then falls back down. The full equation for height at any time is y = y₀ + v₀t − ½gt², where v₀ is the starting velocity (positive if thrown upward, negative if thrown downward) and y₀ is the starting height. The object reaches its maximum height when all upward velocity is used up, which happens at time t = v₀ / g. If the object is launched at an angle rather than straight up or down, you'll want to use our Projectile Motion Calculator instead.
Energy in Free Fall
Energy is always conserved during free fall. At the top, an object has potential energy (PE = mgh), which is stored energy due to its height. You can calculate this precisely with our Potential Energy Calculator. As it falls, that potential energy turns into kinetic energy (KE = ½mv²), which is the energy of motion — use our Kinetic Energy Calculator to explore this in more detail. Right before hitting the ground, nearly all the potential energy has become kinetic energy. The total mechanical energy — potential plus kinetic — stays the same throughout the fall, as long as air resistance is ignored.
The Role of Air Resistance
In real life, air pushes back against a falling object. This push is called air resistance or drag. As an object falls faster, the drag force grows until it equals the pull of gravity. At that point, the object stops speeding up and falls at a constant speed called terminal velocity. Terminal velocity depends on the object's mass, shape, size, and the density of the air. A skydiver in a spread-eagle position has a terminal velocity of about 55 m/s (roughly 120 mph), while a streamlined object like a bullet falls much faster. Understanding the balance between gravitational force and drag force is key — our Force Calculator can help you analyze forces in different scenarios.
Gravity on Other Planets
Gravity is not the same everywhere. On the Moon, gravitational acceleration is only about 1.6 m/s², so objects fall much slower and you could jump much higher. On Jupiter, gravity is a powerful 24.8 m/s², meaning objects fall about 2.5 times faster than on Earth. This is why the calculator lets you pick different celestial bodies — the same drop height produces very different fall times and impact speeds depending on where you are in the solar system. For an extreme example of gravity, our Schwarzschild Radius Calculator lets you explore the gravitational boundaries of black holes.
Real-World Examples of Free Fall
Free fall physics shows up in many everyday and extreme situations. A penny dropped from the Empire State Building (443 meters) takes about 9.5 seconds to reach the ground and hits at roughly 93 m/s without air resistance. In 2012, Felix Baumgartner jumped from 39,045 meters above Earth and reached speeds over 370 m/s before air resistance slowed him down. Galileo's famous experiment at the Leaning Tower of Pisa demonstrated that two objects of different mass hit the ground at the same time when dropped from the same height, proving that gravity accelerates all objects equally. When a falling object strikes the ground, the rapid change in velocity creates a large force — you can analyze this using our Impulse Calculator or Momentum Calculator to understand the impact dynamics.