Drag Force Calculator (Drag Equation)
Enter the speed, drag coefficient and frontal area.
Your numbers
Air at sea level and 15 °C is 1.225; water about 1000
Modern car about 0.25 to 0.35; cyclist 0.9; sphere 0.47
Your results
Drag force (N)
Drag force (N)
—
Power to overcome drag (kW)
—
In horsepower
—
Dynamic pressure (Pa)
—
Drag Force Calculator (Drag Equation) by TheCalcTools
How the Drag Force Calculator (Drag Equation) works
Drag grows with the square of speed: F = ½ρv²CdA. The power needed to push through the air is force × speed, so it grows with the cube of speed.
This is why fuel use rises sharply above about 90 km/h, and why cyclists tuck in to reduce their frontal area.
The formula
F = ½ ρ v² Cd A; P = F v
Worked example
Using the default values shown in the calculator:
| Fluid density (kg/m³) | 1.225 |
|---|---|
| Speed (m/s) | 30 |
| Drag coefficient Cd | 0.3 |
| Frontal area (m²) | 2.2 |
- A car with Cd 0.30 and 2.2 m² at 30 m/s: drag 363.8 N.
- Overcoming it takes 10.91 kW.
Result:
| Drag force (N) | 363.8 |
|---|---|
| Power to overcome drag (kW) | 10.91 |
| In horsepower | 14.6 |
| Dynamic pressure (Pa) | 551.2 |
Frequently asked questions
What is 30 m/s?
108 km/h or about 67 mph.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.