Calculate static aerodynamic thrust, exit airspeed, and absorbed shaft power for airplane, drone, and paramotor propellers.
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A propeller thrust calculator uses actuator disk momentum theory and empirical aerodynamic blade lift formulas to compute the static thrust, propwash exit airspeed, and mechanical horsepower or wattage absorbed by a rotating propeller.
T = \frac{\pi}{2} \left(\frac{D}{2}\right)^2 \rho \cdot v_{\text{pitch}}^2 \quad ; \quad v_{\text{pitch}} = \frac{\text{RPM} \cdot P}{60}Where D is propeller diameter in meters, P is pitch in meters, rho is air density (1.225 kg/m³ at sea level), and v_pitch is theoretical fluid column exit velocity.
Scenario: A 10x4.5 inch propeller spinning at 8,500 RPM at standard sea level.
Diameter: 10 inches (0.254 m), Pitch: 4.5 inches (0.1143 m).
Pitch Exit Airspeed: ~36.3 mph (58.4 km/h).
Calculated Static Thrust: ~1,150 grams (~2.53 lbs / 11.3 N).
Shaft Power Absorbed: ~125 Watts.
Larger propellers accelerate a larger volume of air more gently, which actuator disk theory proves minimizes kinetic energy wasted in the slipstream, maximizing propulsive efficiency.
Static thrust is measured when the aircraft is stationary (zero airspeed). Dynamic thrust is the actual net forward pull produced when the airplane is moving at flight speed.
Thrust is directly proportional to air density. At higher altitudes or higher summer temperatures (high density altitude), propellers produce significantly less thrust.
If blade angle of attack is too steep (excessive pitch at zero forward speed), airflow detaches from the blade surface, creating aerodynamic stall and high noise with lost thrust.
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