Enter the force of drag, the density of the fluid, velocity, and frontal area of the body. The calculator will display the drag coefficient of this object.
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Drag Coefficient Formula
The following formula is used to calculate the drag coefficient of an object.
C_d = \dfrac{F_d}{\tfrac{1}{2}\rho v^2 A}- Where Cd is the drag coefficient
- Fd is the force due to drag
- ρ is the density of the fluid
- v is the velocity (relative to the fluid)
- A is the reference area (commonly the frontal area)
Drag Coefficient Definition
A drag coefficient is a unitless (dimensionless) measure of the resistance to movement through a fluid an object has due to its shape.
How to calculate a drag coefficient?
How to calculate a drag coefficient?
- First, determine the drag force acting on the object
The drag coefficient is often determined experimentally (for example, in a wind tunnel) by measuring the drag force on the object at a known fluid density, speed, and reference area. It can also be estimated using published data and correlations for common shapes, or using computational fluid dynamics (CFD), but experiments are commonly used for validation and highest confidence.
- Next, measure the velocity and density of the fluid
Using your test setup information, or device, determine the velocity of the fluid moving around the object. (This could also be the velocity of the object itself.)
- Next, measure the frontal area
Calculate or measure the frontal area of the object. This is the area exposed to the force of drag.
- Calculate
Calculate the drag coefficient using the information from the steps above.
FAQ
A drag coefficient is a coefficient used to describe how aerodynamic a certain object is. That is, how much force acts on an object moving through a fluid relative to its size and the flow speed.
Drag force can be reduced by lowering the drag coefficient (streamlining/smoothing the shape, controlling flow separation), reducing the reference (frontal) area, reducing speed, or operating in a lower-density fluid. Note: reducing frontal area reduces drag force directly, but it does not inherently reduce the drag coefficient for a given definition of reference area.
