Prop Pitch Calculator

Propeller pitch is the theoretical distance a propeller would advance during one complete revolution if it moved through a solid without slipping. It is commonly stated in inches for marine and small aircraft propellers. This prop pitch calculator derives theoretical pitch from propeller diameter and blade pitch angle, applies an efficiency factor for actual pitch, and estimates thrust and required power from rotational speed and fluid density. A propeller blade follows a helical path. At a given reference diameter, one revolution travels around a circumference equal to pi times diameter while advancing axially by one pitch. The tangent of the blade angle is axial travel divided by circumferential travel, so geometric pitch equals pi multiplied by diameter and the tangent of the pitch angle. The result depends strongly on where along the blade the angle was measured because propeller blades are twisted. Manufacturer pitch is normally based on a defined reference station, often near seventy-five percent of blade radius. Actual pitch is modeled as theoretical pitch multiplied by the entered efficiency factor. This compact adjustment represents slip and other departures from the geometric ideal. The calculator converts actual pitch and RPM into axial advance velocity. It estimates thrust from fluid density, propeller disk area, advance velocity squared, and efficiency, then reports corresponding idealized fluid power. Water density is commonly near 1,000 kg/m³, while dry air near sea level is roughly 1.225 kg/m³. These thrust and power values are simplified comparative estimates, not blade-element or computational-fluid-dynamics predictions. Real performance depends on blade section, blade count, pitch distribution, inflow, advance ratio, hull or airframe interaction, cavitation, compressibility, torque limits, and Reynolds number. Small input changes can produce large force changes because the estimate scales with velocity squared. High rotational speed can increase noise, vibration, cavitation in water, and compressibility losses in air. Designers must use detailed aerodynamic or hydrodynamic analysis to assess thrust, torque, power, cavitation margin, blade loading, and structural stress. Never use this result by itself to size an engine, shaft, or flight-critical propulsion component. This calculator is best suited to geometry checks, rough comparisons, and educational work. Measure diameter consistently, use the angle at the intended blade station, select fluid density for the operating environment, and treat estimated thrust and power as idealized indicators rather than guaranteed performance.