# Free Fall Calculator (h = ½gt²) Compute distance, time, or final velocity for free fall from rest, given any one plus gravity > Canonical page: https://elysiatools.com/en/tools/free-fall-calculator - **Category:** Math & Numbers - **Keywords:** free fall, gravity, acceleration, distance, time, velocity, drop, falling object, physics, mechanics, kinematics ## Overview Free fall is motion under gravity alone, starting from rest (v₀ = 0). Equations (given one of h, t, v — plus g — the other two follow): - Distance: h = ½ · g · t² - Time: t = √(2h/g) = v/g - Velocity: v = g · t = √(2gh) Assumes no air resistance, uniform gravity. g defaults to 9.80665 m/s². ## Inputs - **Solve For** (select) - **Distance (h, m)** (number): leave blank when solving for distance - **Time (t, s)** (number): leave blank when solving for time - **Final Velocity (v, m/s)** (number): leave blank when solving for velocity - **Gravity (g, m/s²)** (number): 9.80665 (Earth). Moon ≈ 1.62, Mars ≈ 3.71 ## When to use - When solving physics homework problems involving objects dropped from rest. - When estimating the height of a structure by timing how long a dropped object takes to hit the ground. - When calculating the impact velocity of a falling object on Earth or other celestial bodies with different gravity values. ## How it works - Select the variable you want to solve for: Distance (h), Time (t), or Final Velocity (v). - Enter the known value for one of the other parameters (distance in meters, time in seconds, or velocity in meters per second). - Adjust the gravity constant if you are calculating for a body other than Earth (defaults to 9.80665 m/s²). - Click calculate to compute the remaining values using the equations h = ½gt², t = √(2h/g), and v = gt. ## Use cases - Physics students verifying kinematic homework solutions for dropped objects. - Educators creating lesson plans and answer keys for introductory mechanics classes. - Hobbyists estimating heights or drop times during outdoor activities like rock climbing. ## Frequently asked questions ### Does this calculator account for air resistance? No, it assumes a pure vacuum where the only force acting on the object is gravity. ### Can I calculate free fall on the Moon or Mars? Yes, you can change the gravity input field to 1.62 m/s² for the Moon or 3.71 m/s² for Mars. ### What is the default value used for gravity? The calculator defaults to Earth's standard gravity, which is 9.80665 m/s². ### Can I input an initial velocity other than zero? No, this calculator is designed specifically for free fall starting from rest where the initial velocity is zero. ### What units should I use for the inputs? 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