Engine
Propeller slip
How much the propeller “slips”: the speed the pitch and revolutions would give, against the speed actually made.
From the propeller drawing
Fill in the fields to see the result.
How it works
In one turn a propeller would advance by its pitch if it moved through a solid. So theoretical speed (kn) = pitch (m) × rpm × 60 / 1,852, and slip = (theoretical − actual) / theoretical.
With the speed over the ground it is the apparent slip (current included); with the speed through the water (log) it is closer to the real slip. A rising slip in the same conditions points to fouling, a damaged propeller or a heavier load. Negative apparent slip usually means a following current.
For training and cross-checking. Not a substitute for approved navigation equipment, nautical publications and the ship’s own procedures. Calculations run in your browser and nothing you type is stored; a PDF you download is made on our server and not kept.
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