Prop Pitch Calculator

Your details

Choose which variable to calculate. Provide values for all the others.
The theoretical distance the propeller advances per revolution through a solid medium.
in
Engine crankshaft speed at wide-open throttle (WOT).
RPM
Ratio of engine RPM to propeller shaft RPM (e.g., 1.87 means 1.87 engine turns per prop turn).
:1
How much the propeller slips through the water versus a solid medium. Typically 10-20% at top speed.
%
Result
49.72

The calculated variable

Variable solvedBoat speed (mph)
Theoretical speed (no slip)58.49
Prop shaft RPM2,941
Pitch in inches21
49.72 %
Race<5Performance5-15Normal15-25High slip25-40Excessive40+

Estimated top speed: 49.7 mph

  • At 15% slip your propeller loses 15.0% of its theoretical thrust through the water.
  • Theoretical no-slip speed would be 58.5 mph. Slip accounts for the 8.8 mph difference.
  • Prop shaft is spinning at 2941 RPM (engine RPM divided by gear ratio).

Next stepRemember that these calculations assume wide-open-throttle conditions at the correct pitch angle for your boat and load. Real-world conditions such as hull fouling, payload, and sea state all shift the result.

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