Propeller Size Calculator for
Displacement and Semi-Displacement Hulls

Enter waterline length
in feet
Enter beam at the waterline
in feet
Enter moulded hull draft (excluding keel)
in feet
Enter vessel displacement weight
in pounds
Enter number of engines (shaft lines)
(max 2)
Enter maximum rated horsepower (per engine)
Enter maximum rated engine RPM
Enter gear ratio
Enter number of shaft bearings
per shaft
Enter desired maximum speed


This calculator is free to use as often as you wish.
The calculations and results are based on imperical data and formulas.
The results are only as acurate as the data you enter.
The calculated propeller sizes are based on standard propeller designs;
2 blade = 30% blade area ratio
3 blade = 50% blade area ratio
4 blade = 69% blade area ratio
What it will do

Calculate a propeller size based on the data you enter
Calculate a vessel speed based on the available horsepower
Calculate the horsepower required for a desired speed

What it won't do

No calculations for cavitation
No calculations for blade area ratio
No calculations for towing, bollard thrust, etc.