Calculation
Fw = ½·cw·A·ρ·v²
Drag force grows with the square of speed; doubling speed quadruples the force.
Dubbel Kraftfahrzeugtechnik Q 2.1.2: FL = cW·A·ρ·v²/2 (Pkw cW 0,25–0,4, A 1,5–2,5 m²); Mechanik B 6.6.4, Gl. (35)
Vehicle aerodynamic drag force
Drag force grows with the square of speed; doubling speed quadruples the force.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Drag force Fw — Aerodynamic force opposing motion at the considered speed.
- Drag coefficient cw — Shape-dependent dimensionless coefficient; modern passenger cars are roughly 0.25 to 0.35.
- Frontal area A — Projected cross-sectional area of the vehicle in the direction of travel.
- Air density ρ — Density of ambient air; about 1.2 kg/m³ at 20 °C and sea level.
- Vehicle speed v — Speed relative to the surrounding air (higher in headwind).
Example
cw=0.3, A=2.2 m², ρ=1.2 kg/m³ and v=108 km/h (30 m/s) give Fw≈356 N.
Assumptions and limits
Steady flow with no crosswind, speed relative to still air and constant cw over the speed range; lift, ground effect and unsteady effects are excluded.
Understand Vehicle aerodynamic drag force
This calculator determines a vehicle's aerodynamic drag force, the driving resistance that dominates at higher speed, from shape, size and travel speed.
What does this quantity describe?
Drag force follows from Fw=½·cw·A·ρ·v², where cw captures vehicle shape, A frontal area and ρ air density.
Formula and variables
Fw = ½·cw·A·ρ·v²
Fw = ½·cw·A·ρ·v²
| Symbol / input | Meaning |
|---|---|
| Drag force Fw | Aerodynamic force opposing motion at the considered speed. |
| Drag coefficient cw | Shape-dependent dimensionless coefficient; modern passenger cars are roughly 0.25 to 0.35. |
| Frontal area A | Projected cross-sectional area of the vehicle in the direction of travel. |
| Air density ρ | Density of ambient air; about 1.2 kg/m³ at 20 °C and sea level. |
| Vehicle speed v | Speed relative to the surrounding air (higher in headwind). |
Choose the inputs correctly
cw is the vehicle's drag coefficient, A the projected frontal area, ρ air density and v speed relative to the air.
How to use the calculator
Take cw and A from the vehicle datasheet; use ρ=1.2 kg/m³ for standard conditions unless more precise values are available.
Worked example
cw=0.3, A=2.2 m², ρ=1.2 kg/m³ and v=108 km/h (30 m/s) give Fw≈356 N.
Understand the result and units
Since Fw grows with the square of v, drag dominates total driving resistance far more at highway speed than at city speed.
cw is dimensionless, A an area, ρ a density and v a speed. Fw is output as a force.
Typical applications
Estimating driving resistance for range, consumption and drivetrain sizing calculations, and comparing different vehicle shapes.
Assumptions, limits and common mistakes
Steady flow with no crosswind, speed-independent cw and speed relative to still air; lift, ground effect, gusts and unsteady flow are excluded.
Common mistake: Do not use ground speed instead of speed relative to the air when there is significant head- or tailwind.
Frequently asked questions
What is “Vehicle aerodynamic drag force” used for?
Estimating driving resistance for range, consumption and drivetrain sizing calculations, and comparing different vehicle shapes.
Where do the input values come from?
cw is the vehicle's drag coefficient, A the projected frontal area, ρ air density and v speed relative to the air.
What does the result not cover?
Steady flow with no crosswind, speed-independent cw and speed relative to still air; lift, ground effect, gusts and unsteady flow are excluded.