Drag Force Calculator (Air Resistance)
Aerodynamic drag on a car, bike or any object at a given speed, the power needed to overcome it and the energy it costs per 100 km.
Results
The dashed line marks the value you entered.
What this tool does
Air resistance grows with the square of speed, and the power to push through it with the cube — going from 100 to 130 km/h takes about 2.2 times the power for the air alone. The drag coefficient describes the shape and the frontal area the size; their product, CdA, is what actually counts, which is why a small car with an ordinary Cd can beat a large one with an excellent Cd. The energy per 100 km is the part of a vehicle's consumption spent on air, before tyres, drivetrain and hills. Wind is added to the speed through the air; the power uses the speed over the ground.
Formula
F = ½ ρ v² C_d A · P = F × v
Variables
| Symbol | Meaning | Unit |
|---|---|---|
v | Speed | km/h |
cd | Drag coefficient | — |
a | Frontal area | m² |
ro | Air density | kg/m³ |
w | Headwind (negative for tailwind) | km/h |
F | Drag force | N |
P | Power needed against drag | kW |
EK | Energy per 100 km, air alone | kWh |
CA | Drag area CdA | m² |
Worked example
- Speed100 km/h
- Drag coefficient0.3
- Frontal area2.2 m²
- Air density1.225 kg/m³
- Headwind (negative for tailwind)0 km/h
- Drag force311.9 N
- Power needed against drag8.66 kW
- Energy per 100 km, air alone8.66 kWh
- Drag area CdA0.660 m²
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.