Drag Coefficient Calculator

The resistance force acting on any object moving through air, water, or another fluid is called drag — and the Drag Coefficient Calculator computes exactly how large that force is. Enter your velocity, reference area, fluid density, and select your object shape (sphere, cylinder, flat disk, streamlined body, or custom) to get the Drag Force in Newtons. Secondary outputs include Reynolds Number, Dynamic Pressure, and Effective Drag Area.

m/s

Relative velocity between object and fluid

m²

Cross-sectional area perpendicular to motion

Depends on object shape (sphere: 0.47, cylinder: 1.2, disk: 1.28)

kg/m³

Air at sea level: 1.225 kg/m³, Water: 1000 kg/m³

Units System

Results

Drag Force

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Reynolds Number

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Dynamic Pressure

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Effective Drag Area

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Frequently Asked Questions

What is the equation for drag force?

The drag force equation is Fd = 1/2 × ρ × u² × A × Cd, where Fd is drag force, ρ is fluid density, u is velocity, A is reference area, and Cd is the drag coefficient.

How can I calculate the drag coefficient of an object?

The drag coefficient depends on the object's shape and surface roughness. Common values are: sphere (0.47), long cylinder (1.2), flat disk (1.28), and streamlined bodies (0.04-0.1).

What is the reference area in drag calculations?

The reference area is the cross-sectional area of the object perpendicular to the direction of motion. For a sphere, it's πr², and for a cylinder, it's the projected area facing the flow.

How does velocity affect drag force?

Drag force increases with the square of velocity. Doubling the speed results in four times the drag force, making high-speed motion increasingly energy-intensive.

What factors influence the drag coefficient?

The drag coefficient is influenced by object shape, surface roughness, Reynolds number, and flow conditions. Streamlined shapes have lower coefficients than blunt objects.

How can I find the terminal velocity of a falling object?

Terminal velocity occurs when drag force equals gravitational force. Set Fd = mg and solve for velocity: v = √(2mg/(ρACd)), where m is mass and g is gravitational acceleration.

What is the difference between form drag and skin friction?

Form drag results from pressure differences around an object's shape, while skin friction comes from fluid viscosity at the surface. The drag coefficient accounts for both effects.