BYTETOOLS

Free Fall Calculator

Work out fall time, drop height or impact speed from v = √(2gh) and h = ½gt², with gravity presets for the Moon and Mars and an impact energy line.

100 m
Drop height
4.516 s
Fall time
44.2869 m/s
Impact speed
—
Impact energy

Working

  • v = √(v₀² + 2gh) = √(0² + 2 × 9.80665 × 100) = 44.2869 m/s
  • t = √(2h ÷ g) = √(2 × 100 ÷ 9.80665) = 4.516 s
  • Average speed over the fall = h ÷ t = 22.1435 m/s.

Also handy: 159.433 km/h, 99.067 mph, 328.084 ft of drop.

This is the drag-free (vacuum) model, so it over-predicts real impact speeds. In air an object accelerates only until drag balances weight, and from then on it falls at a constant terminal velocity — roughly 55 m/s for a skydiver in a belly-to-earth position and about 9 m/s for a raindrop. Below about 20 metres the difference is small for a dense compact object; for anything light, large or falling a long way, treat these numbers as an upper bound rather than a prediction.

What is the Free Fall Calculator?

In drag-free fall from rest an object reaches v = √(2gh) after falling a height h, taking t = √(2h ÷ g). On Earth with g = 9.80665 m/s², a 100 m drop takes 4.52 s and ends at 44.3 m/s.

  • Solves from any one of drop height, fall time or impact speed
  • Gravity presets for Earth, the Moon, Mars, Venus and Jupiter, plus custom g
  • Optional non-zero initial velocity for thrown as well as dropped objects
  • Impact kinetic energy ½mv² when you supply a mass
  • Speeds also shown in km/h and mph, heights in feet
  • Everything computed in your browser, with no uploads

How to use the Free Fall Calculator

  1. 1

    Choose what you already know: the drop height, the fall time or the impact speed.

  2. 2

    Pick a gravity preset or type your own value of g in metres per second squared.

  3. 3

    Enter your known value with its unit, and set an initial downward speed if the object was thrown.

  4. 4

    Optionally add a mass to see the kinetic energy at impact.

  5. 5

    Read the height, time, speed and energy tiles, and copy the working with one click.

About the Free Fall Calculator

The ByteTools Free Fall Calculator links the three quantities of a vertical drop — height, time and impact speed — so you only need to know one of them. Tell it which one you have and it applies the matching kinematic equation, whether that is h = v₀t + ½gt², v = √(v₀² + 2gh) or t = (v − v₀) ÷ g, and shows the substitution it used.

Gravity is selectable, with presets for Earth at 9.80665 m/s², the Moon at 1.62, Mars at 3.72, Venus at 8.87 and Jupiter at 24.79, plus a custom box for any other value. You can add a non-zero initial downward speed for something thrown rather than dropped, and an optional mass turns the answer into an impact kinetic energy of ½mv².

All the arithmetic happens locally in your browser using plain JavaScript. Nothing is uploaded to a server and nothing is stored between sessions, so the numbers update instantly as you type and the calculator keeps working after you go offline.

Frequently asked questions

How do you calculate the speed of a falling object?

For a drop from rest the impact speed is v = √(2gh), where g is gravity and h is the drop height. Falling 100 m on Earth gives √(2 × 9.80665 × 100) = 44.3 m/s, which is about 159 km/h.

How long does it take to fall a given distance?

From rest the time is t = √(2h ÷ g), so a 100 m drop on Earth takes about 4.52 seconds. Doubling the height does not double the time — it multiplies it by only √2, roughly 1.41.

Do heavier objects fall faster?

In a vacuum they do not: mass cancels out of the equations, so a feather and a hammer hit the ground together. In air, heavier and denser objects usually do fall faster because drag matters less relative to their weight.

Does this calculator include air resistance?

No — it uses the drag-free vacuum model, so it over-predicts real impact speeds. In air an object accelerates only until drag balances weight and then falls at a constant terminal velocity, roughly 55 m/s for a belly-to-earth skydiver and about 9 m/s for a raindrop.

What value of gravity should I use?

Standard gravity is 9.80665 m/s², which is the usual textbook value for Earth. Local gravity varies from about 9.78 at the equator to 9.83 at the poles, and the presets cover the Moon, Mars, Venus and Jupiter for other worlds.

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