Our drag Coefficient calculator allows you to work out the force on an object moving through air or any other fluid.
Every moving object experiences a resisting force known as drag, and the drag coefficient is a measure of how streamlined, or resistant that object is.
What is Drag Force and How to Calculate Drag?
Hi Guys, Do you want know what is drag coefficient formula? Are you curious about how drag relates to velocity, fluid density, and surface area? Look no further, because you’ve come to the right place!”
Drag Coefficient Calculator
Cd = (2 × Fd) ÷ (ρ × v² × A)
Where:
• Cd = Drag Coefficient (dimensionless)
• Fd = Drag Force (N)
• ρ = Fluid Density (kg/m³, ~1.225 for air)
• v = Velocity (m/s)
• A = Reference Area (m²)
📘 Explanation of Terms in Drag Formula
The drag coefficient formula is:
Cd = (2 × Fd) ÷ (ρ × v² × A)
- Cd → Drag Coefficient (dimensionless, indicates aerodynamic efficiency).
- Fd → Drag Force (N), the resisting force acting opposite to the motion of the body.
- ρ (rho) → Fluid Density (kg/m³), mass per unit volume of the fluid (air ≈ 1.225 kg/m³ at sea level).
- v → Velocity (m/s), the speed of the object relative to the fluid.
- A → Reference Area (m²), usually the frontal (cross-sectional) area facing the flow.
Illustration: Object (car) facing airflow, showing drag force, velocity, and reference area.
📘 Example Problem
Problem: Calculate the drag coefficient of a car experiencing a drag force of 1000 N while traveling at 30 m/s. The car has a frontal area of 2.2 m², and the air density is 1.225 kg/m³.
Solution Steps:
- Step 1: Given Data
Fd = 1000 N, ρ = 1.225 kg/m³, v = 30 m/s, A = 2.2 m² - Step 2: Write Formula
Cd = (2 × Fd) ÷ (ρ × v² × A) - Step 3: Substitute Values
Cd = (2 × 1000) ÷ (1.225 × 30² × 2.2) - Step 4: Simplify
Cd = 2000 ÷ (1.225 × 900 × 2.2)
Cd = 2000 ÷ 2425.5 - Step 5: Final Answer
Cd ≈ 0.825
📊 Drag Coefficient Reference Table
| Object | Typical Cd Value |
|---|---|
| Sports Car | 0.30 – 0.35 |
| Truck / Bus | 0.60 – 0.90 |
| Bicycle | 0.70 – 1.00 |
| Sphere | 0.45 – 0.50 |
| Flat Plate (perpendicular) | ~1.28 |
| Airfoil (streamlined) | 0.04 – 0.10 |
FAQs
1. What is a good drag coefficient value?
A good drag coefficient is usually between 0.25 – 0.35 for modern cars. The lower the value, the more aerodynamic the object is.
2. Does drag coefficient depend on speed?
No — the drag coefficient itself doesn’t change with speed. But the total drag force increases with velocity, since it depends on v²
3. Why is drag coefficient important?
Because it tells us how much resistance an object faces. Lower drag means higher efficiency, better fuel economy, and improved performance in vehicles.
4. Is drag coefficient dimensionless?
Yes! Cd has no units — it’s a pure number that compares drag to fluid density, velocity, and area.