Drag Coefficient Calculator Formula

Understand the math behind the drag coefficient calculator. Each variable explained with a worked example.

Use the Drag Coefficient Calculator

Formulas Used

Drag Force

drag_force = 0.5 * cd * density * area * pow(velocity, 2)

Dynamic Pressure

dynamic_pressure = 0.5 * density * pow(velocity, 2)

Variables

VariableDescriptionDefault
cdDrag Coefficient (Cd)0.47
densityFluid Density(kg/m3)1.225
areaReference Area(m2)0.01
velocityVelocity(m/s)20

How It Works

Aerodynamic Drag Force

Drag opposes the motion of an object through a fluid.

Formula

F_d = 0.5 Cd rho A v^2

  • *Cd* = drag coefficient (shape-dependent, dimensionless)
  • *rho* = fluid density
  • *A* = reference frontal area
  • *v* = velocity relative to fluid

    • Common Cd values: sphere 0.47, streamlined body 0.04, flat plate 1.28, car 0.25-0.45.

    Worked Example

    Sphere (Cd = 0.47) of cross-section 0.01 m2 in air at 20 m/s.

    cd = 0.47density = 1.225area = 0.01velocity = 20
    1. 01F_d = 0.5 * 0.47 * 1.225 * 0.01 * 400
    2. 02F_d = 0.235 * 1.225 * 4
    3. 03F_d = 1.152 N

    Ready to run the numbers?

    Open Drag Coefficient Calculator