Drag Force Calculator (Aerodynamic / Fluid Drag)

The quadratic drag equation gives the force a fluid exerts on an object moving through it: F = ½ × Cd × ρ × A × v², where ρ is the fluid's density, A is the object's frontal (cross-sectional) area facing the flow, Cd is its dimensionless drag coefficient (how 'slippery' its shape is), and v is its speed relative to the fluid. This is the same force terminal-velocity-calculator's formula sets equal to weight to solve for the speed at which the two balance — this calculator instead reports the drag force directly at whatever speed you give it.

Because the force grows with the square of velocity, doubling your speed quadruples the drag force, while doubling the frontal area or the drag coefficient only doubles it. Velocity and frontal area carry this page's metric/imperial toggle; fluid density and the drag coefficient are left as plain, un-toggled inputs since kg/m³ and a dimensionless shape factor are already the standard units used worldwide in aerodynamics.