Drag Equation Calculator
Calculate drag force on objects moving through fluids using the drag equation
Drag Force Parameters
Select fluid or use custom density
Density of the fluid medium
Velocity of object relative to fluid
Select object shape for drag coefficient
Dimensionless drag coefficient
Cross-sectional area perpendicular to flow
Drag Force Results
Drag Force
Additional Parameters
Formula used: Fd = ½ × ρ × v² × A × Cd
Input values: ρ=1.225kg/m³, v=0.00m/s, A=0.0000m², Cd=0.47
Flow Analysis
Example Calculation
Skydiver with Parachute
Fluid: Air (ρ = 1.225 kg/m³)
Velocity: 20 m/s
Parachute area: 7 m²
Drag coefficient: 1.3 (parachute)
Calculation
Fd = ½ × ρ × v² × A × Cd
Fd = ½ × 1.225 × 20² × 7 × 1.3
Fd = ½ × 1.225 × 400 × 7 × 1.3
Fd = 2,191.5 N
Drag Coefficient Values
Streamlined
Cd = 0.04
Highly aerodynamic shapes
Sphere
Cd = 0.47
Smooth sphere
Cylinder
Cd = 0.82
Long cylinder, cross flow
Cube
Cd = 1.05
Bluff body
Applications
Aerospace
Aircraft and spacecraft design
Automotive
Vehicle aerodynamics and fuel efficiency
Sports
Equipment design and performance
Civil Engineering
Building and bridge wind loads
Calculation Tips
Use cross-sectional area perpendicular to flow direction
Drag coefficient depends on Reynolds number and shape
Consider surface roughness for accurate Cd values
Account for compressibility at high velocities
Understanding the Drag Equation
What is Drag Force?
Drag force is the resistance force that opposes the motion of an object through a fluid (liquid or gas). It acts parallel to and in the opposite direction of the object's velocity relative to the fluid.
Key Factors
- •Fluid density (ρ) - denser fluids create more drag
- •Velocity² (v²) - drag increases with square of velocity
- •Reference area (A) - larger cross-section increases drag
- •Drag coefficient (Cd) - depends on object shape
Drag Equation
Fd = ½ × ρ × v² × A × Cd
- Fd: Drag force (N)
- ρ: Fluid density (kg/m³)
- v: Relative velocity (m/s)
- A: Reference area (m²)
- Cd: Drag coefficient (dimensionless)
Note: The ½ factor comes from the dynamic pressure term in fluid mechanics
Types of Drag
Form Drag
Due to pressure difference around object
Dominant for bluff bodies like spheres, cubes
Skin Friction
Due to viscous effects at surface
Important for streamlined bodies
Induced Drag
Due to lift generation in 3D flow
Significant for wings and airfoils