🌀 Prop Slip Calculator

Propeller Slip

Slip is the percentage difference between a propeller’s theoretical (no-slip) pitch speed and its actual measured speed through the air or water: Slip% = ((Theoretical − Actual) / Theoretical) × 100.

Some slip is normal and necessary — a propeller with zero slip would generate no thrust, since it needs to “push against” the fluid to move forward. Typical boat propellers run 10–25% slip, while aircraft propellers often run lower. Excessive slip usually indicates the pitch or diameter is mismatched to the application, or that the craft is under heavy load.