Calculate thrust required, drag coefficient, air density, velocity or frontal area from the drag equation with metric and imperial units.
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Thrust Required Formula
The calculator uses the drag equation. For steady, constant-speed motion, thrust required is equal to aerodynamic drag.
T = 0.5*C_d*rho*V^2*A
Rearranged forms:
C_d = (2*T)/(rho*V^2*A)
rho = (2*T)/(C_d*V^2*A)
V = sqrt((2*T)/(C_d*rho*A))
A = (2*T)/(C_d*rho*V^2)
- T = thrust required, in newtons or pounds-force
- Cd = drag coefficient, unitless
- rho = air density
- V = velocity
- A = frontal area
This calculation assumes thrust required equals aerodynamic drag. It does not include rolling resistance, climb force, acceleration, wind, drivetrain losses, or propeller efficiency.
Useful Tables
| Condition | Typical air density | Notes |
|---|---|---|
| Sea level, standard atmosphere | 1.225 kg/m³ | Common default value |
| Warm low-altitude day | 1.15 to 1.20 kg/m³ | Lower density reduces drag |
| High altitude | Below 1.0 kg/m³ | Depends strongly on altitude and temperature |
| Object type | Typical drag coefficient | Comment |
|---|---|---|
| Streamlined car | 0.20 to 0.35 | Varies with shape and underbody design |
| SUV or truck | 0.35 to 0.60 | Larger frontal area also increases thrust required |
| Cyclist upright | 0.7 to 1.1 | Position changes the result a lot |
| Flat plate facing flow | 1.1 to 1.3 | High-drag reference shape |
Result Notes
Velocity has the largest effect because it is squared. If speed doubles, thrust required for aerodynamic drag becomes about four times larger.
Use consistent, real-world inputs. A small error in frontal area or drag coefficient can noticeably change the final thrust value.
