About the Free Fall Calculator
When an object is dropped and nothing but gravity acts on it, it falls faster every second. This calculator works out how long a fall takes and how fast the object is moving when it lands. You can enter the height of the drop or the time of the fall, and you can choose the gravity of Earth, the Moon, Mars, Venus or Jupiter. Type either the height or the time of the fall, and the gravity and the free fall appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Free Fall Calculator
- 1Enter either the height or the time of the fall, and the gravity.
- 2Pick the units or options from the menus if the free fall tool offers them.
- 3Read the free fall in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the free fall
Physics students use free fall to practise the equations of motion. Climbers and engineers use it to estimate impact speeds, and anyone curious about a bridge, a cliff or a well can time a dropped stone and work out how far down it went.
Choosing another planet shows how gravity changes everything: on the Moon the same 20 m drop takes about five seconds, and the landing speed is a gentle 8 m/s. That is why astronauts seem to float.
How the free fall is worked out
Time = √(2 × height ÷ g). Speed = g × time. Height = ½ × g × time². These assume the object starts at rest and there is no air resistance. Dropping something from 20 m on Earth takes √(2 × 20 ÷ 9.80665) = 2.02 s, and it lands at 19.81 m/s, about 71 km/h. Falling for 3 seconds covers ½ × 9.80665 × 9 = 44.13 m and reaches 29.42 m/s.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Enter the height or the time
- Five different gravities
- Shows km/h, mph and feet
Mistakes to avoid with free fall
Real objects meet air resistance. A feather, a parachute or a sheet of paper is slowed a lot, and even a person reaches a top speed of about 55 m/s in a belly-down fall. The formulas here are exact in a vacuum and good for short drops of compact, heavy objects.
On phone and computer
On a phone, type into the boxes one after another and read the free fall underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the free fall move. The free fall calculator works the same on both. When something is thrown instead of dropped, use Projectile Motion Calculator. Potential Energy Calculator shows the energy at the starting height, Speed Calculator compares the speeds, and Weight on Other Planets Calculator shows how the fall changes on other worlds.
Features
- Starts from rest
- Vacuum assumption
- Speed grows steadily with time
- Clear messages when the free fall inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate free fall?
Time = √(2 × height ÷ g). Speed = g × time. Height = ½ × g × time². These assume the object starts at rest and there is no air resistance. Dropping something from 20 m on Earth takes √(2 × 20 ÷ 9.80665) = 2.02 s, and it lands at 19.81 m/s, about 71 km/h. Falling for 3 seconds covers ½ × 9.80665 × 9 = 44.13 m and reaches 29.42 m/s.
What is the formula for free fall?
Time = √(2 × height ÷ g). Speed = g × time. Height = ½ × g × time². These assume the object starts at rest and there is no air resistance. The free fall calculator applies it exactly and rounds only the displayed answer to six significant figures.
Does mass change how fast something falls?
Not in a vacuum. All objects fall with the same acceleration, which is why a hammer and a feather landed together on the Moon.
What is the speed of a 10 m fall?
About 14 m/s on Earth, or around 50 km/h, after 1.43 seconds.
Why does the answer ignore air resistance?
Because it depends on shape and size. For compact dense objects over short drops the error is small.
Is this free fall calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.