MotionLab

Drag Force Calculator

The resistive force air exerts on anything moving through it — cars, cyclists, aircraft, and more.

Drag coefficient (Cd)

Air density (kg/m³)

Velocity (m/s)

Frontal area (m²)

Drag force (N)

330.75

F = ½ρv²ACd

What you entered

Drag coefficient (Cd): 0.3Air density (kg/m³): 1.225Velocity (m/s): 30Frontal area (m²): 2

1
F = ½ρv²ACd
0.5 × 1.225 × 30² × 2 × 0.3= 330.75 N

Result

Drag force (N): 330.75

At 30 m/s with Cd=0.3, drag force is 330.75 N.

Aerodynamic drag at different speeds

Drag is half the air density times the drag coefficient, the frontal area and the velocity squared, at 1.225 kg/m3.

Drag coefficient	Velocity (m/s)	Area (m2)	Drag force (N)
0.47	50	0.01	7.20
1	10	0.7	42.88
0.3	20	2.2	161.70
0.3	30	2.2	363.83
1.05	25	1.5	602.93

Rows three and four are the same car at 72 km/h and 108 km/h, and the drag more than doubles for a 50% speed increase because velocity is squared. Since power equals force times velocity, the power needed to overcome drag grows with the cube of speed - which is why fuel economy collapses at motorway speeds and why the last few km/h of top speed are so expensive. A modern car has a drag coefficient near 0.3, a cyclist about 1.0, and a flat plate around 1.28.

Drag grows with the square of speed

Doubling your speed quadruples drag force — this is why fuel economy drops sharply at highway speeds, and why aerodynamics matters far more at high speed than around town.

Drag coefficient depends on shape

A streamlined shape (like a teardrop) has a much lower drag coefficient than a flat, blunt shape moving through the same fluid — this is why sports cars and cyclists in aero positions are shaped the way they are.

Frequently asked questions

A car driving at 100 km/h (27.8 m/s) has frontal area 2.2 m² and Cd = 0.30. What's the drag force?

F = ½ρv²ACd = ½ × 1.225 × 27.8² × 2.2 × 0.30 = ½ × 1.225 × 772.84 × 0.66 = 312.5 N. At 200 km/h, drag quadruples to ~1,250 N — this is why highway fuel consumption rises sharply.

How much power does a cyclist need to overcome drag at 40 km/h?

At 40 km/h (11.1 m/s), with A ≈ 0.5 m² and Cd ≈ 0.9: F = ½ × 1.225 × 123.2 × 0.45 = 33.9 N. Power = F × v = 33.9 × 11.1 = 376 W. That's why maintaining 40 km/h on a bike is genuinely hard — most recreational cyclists produce about 100-200 W.

How is drag force related to terminal velocity?

Terminal velocity is the speed where drag equals weight. Set ½ρv²CdA = mg and solve for v: v_t = √(2mg/(ρCdA)). The drag force calculator gives you the force at any speed; terminal velocity is where that force curve intersects the weight line. See the terminal velocity calculator.