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Terminal Velocity Calculator

This terminal velocity calculator gives the top speed of a falling object from its mass, cross-sectional area, drag coefficient and the density of the fluid it falls through. The result shows in metres per second and in km/h, and it updates as you type. The defaults, an 80 kg skydiver falling belly-down in air, give 42.8 m/s (154 km/h). Everything runs in your browser and nothing is uploaded.

How to use the terminal velocity calculator

Fill in the four fields under the result card. The card at the top shows Terminal velocity in m/s, big, with km/h below it. If any field is empty or not above zero, the card shows "-" and the line "Enter values above zero" until every field has a valid number.

Mass (kg): the mass of the falling object. Default 80.
Cross-sectional area (m²): the area the object presents to the flow, seen from below. Default 0.7.
Drag coefficient: set by shape, with no unit. Default 1.
Fluid density (kg/m³): the density of the air or liquid. Default 1.225, air at sea level.

To change gravity, open Advanced: gravity. Pick a place under Falling on, or type your own value into the gravity field in m/s². Typing a value that does not match a listed body switches the dropdown to Custom.

The terminal velocity formula

An object reaches terminal velocity when drag pushes up exactly as hard as gravity pulls down, so it stops accelerating. Setting weight m g equal to drag ½ ρ A Cd v² and solving for speed gives:

Formula v = √(2 m g / (ρ A Cd))
m = mass (kg), g = gravity (m/s²), ρ = fluid density (kg/m³), A = cross-sectional area (m²), Cd = drag coefficient
km/h = m/s × 3.6

Because speed depends on the square root, doubling the mass raises terminal velocity by only about 41%, and quadrupling the area halves it. That is why a parachute, which is mostly extra area and drag, slows a fall so much.

Drag coefficient values to start with

The drag coefficient is the hardest input to know, and it is the one that moves the answer most. These are typical figures; the hint under the field gives the first three.

Shape	Drag coefficient (about)
Sphere	0.47
Skydiver, belly-down	1.0
Flat disc facing the flow, such as a coin	1.1
Streamlined body	0.04

Fluid density: air, water and others

Air at sea level is 1.225 kg/m³ and fresh water is about 1000 kg/m³, the two values the hint under the field names. Air thins with altitude, so a fall from high up is faster at first and slows as the air gets denser. This calculator uses one fixed density for the whole fall, so use a value that fits where most of the fall happens.

Terminal velocity on the Moon, Mars and other planets

The Falling on list sets gravity for ten bodies, listed below. Gravity is only half the story: most of these places have a very different atmosphere from Earth's, so the speed depends on the local air too.

Falling on	Gravity (m/s²)
Earth	9.81
Moon	1.62
Mars	3.71
Venus	8.87
Mercury	3.7
Jupiter	24.79
Saturn	10.44
Uranus	8.69
Neptune	11.15
Titan	1.35

For a real answer, set Fluid density to the local atmosphere as well. The Moon and Mercury have almost no air, so there is no terminal velocity there at all. Mars has air about 60 times thinner than Earth's, near 0.020 kg/m³ at the surface, so the same 80 kg, 0.7 m² object with Cd 1 falls at roughly 206 m/s there, far faster than on Earth despite the lower gravity.

The result is an estimate. It assumes a constant fluid density and a fixed drag coefficient, and it has no buoyancy term. Buoyancy is negligible in air but matters for a dense object falling in water. Real falls vary: a skydiver changes posture, a raindrop flattens as it falls.

Worked examples

Skydiver, belly-down (the defaults) Mass 80, area 0.7, Cd 1, density 1.225
Terminal velocity: 42.8 m/s, 154 km/h

Penny, flat face down Mass 0.0025 kg, area 0.000285 m², Cd 1.17, density 1.225
Terminal velocity: about 11 m/s, about 39 km/h

Raindrop, 2 mm across Mass 0.0000042 kg, area 0.0000031 m², Cd 0.47, density 1.225
Terminal velocity: about 6.7 m/s, about 24 km/h

Frequently asked questions

What is the terminal velocity of a human?

For a skydiver lying belly-down it is roughly 40 to 55 m/s (about 145 to 200 km/h), and the defaults here give 42.8 m/s, or 154 km/h (about 96 mph). It depends on mass, body position and air density. Pulling the arms and legs in reduces the area and drag coefficient and raises the speed, so a head-down dive can pass 70 m/s.

What is the terminal velocity formula with the drag coefficient?

v = √(2 m g / (ρ A Cd)), where m is mass, g is gravity, ρ is fluid density, A is cross-sectional area and Cd is the drag coefficient. It comes from setting weight equal to drag, ½ ρ A Cd v². Enter the four values above and the calculator applies it for you.

Is there terminal velocity on the Moon?

No, because the Moon has no atmosphere to produce drag, so a falling object keeps accelerating until it lands. Choosing Moon under Falling on lowers gravity to 1.62 m/s², but you must also set a realistic fluid density; with Earth's air it only shows how fast the object would fall if the air were there.

What is terminal velocity on Mars compared with Earth?

Gravity on Mars is 3.71 m/s², but the air is about 60 times thinner, near 0.020 kg/m³. Choose Mars under Falling on and set Fluid density to 0.020, and the default object falls at roughly 206 m/s, about five times faster than on Earth. Thin air matters more than low gravity.

What is the terminal velocity of a raindrop?

A drop 2 mm across falls at about 6.5 to 7 m/s. Use a mass of 0.0000042 kg, an area of 0.0000031 m², a drag coefficient of 0.47 and air density 1.225 to get 6.7 m/s. Larger drops flatten and break up, and tiny drizzle drops fall much more slowly, so this estimate only suits drops of about that size.

What is the terminal velocity of a penny?

About 11 m/s (roughly 39 km/h) for a US penny falling flat. A penny is 2.5 g with a face area near 0.000285 m², and a flat disc has Cd close to 1.17. A tumbling coin spends time edge-on, so real falls vary.

How do I find the terminal velocity in water?

Set Fluid density to about 1000 for fresh water and enter the object's mass, area and drag coefficient. The result is the sinking speed once drag balances weight. This calculator has no buoyancy term, so for a dense object in water it overstates the speed; the lift from displaced water is small for lead and large for a light object.

What drag coefficient should I use?

Pick the nearest shape: a sphere is about 0.47, a skydiver belly-down about 1.0, a flat disc facing the flow about 1.1 and a streamlined body about 0.04. These are rough, so test a range and see how much the result moves. Because speed scales with one over the square root of Cd, a 20% error in Cd changes speed by about 10%.