PROP PITCH SPEED
Theoretical top speed from prop pitch and RPM, with slip — for boats and aircraft
PROP & RPM
Pitch (inches)
RPM
Slip (%)
Theoretical (no slip)
—
Realistic (mph)
—
Realistic (km/h)
—
Realistic (knots)
—
—
PITCH, RPM & SLIP
THE FORMULA
A prop theoretically advances its pitch once per turn. Speed (no slip) = pitch × RPM. Multiply out the units and you get distance per minute, then per hour.
SLIP
Real props never reach theoretical speed — water and air give way. Boats: 15–25% slip; efficient aircraft props ~10–20%. Higher slip = more thrust, lower top speed.