What does propeller pitch mean?

Pitch is the theoretical distance the propeller would advance in one revolution if there were no slippage, like a screw moving through a solid. A 6-inch pitch prop moves forward 6 inches per revolution in theory. Higher pitch = more speed but more load on the motor.

Why is theoretical speed different from actual speed?

Theoretical speed assumes zero slippage. The propeller always advances less than its geometric pitch because some slip is needed to generate thrust. This calculator applies a (1 − slip) factor: the 75% default means roughly 25% slip, within the typical 10-25% range for a well-matched RC prop. The factor here is a speed-reduction (slip) figure, not the same thing as true propulsive efficiency (thrust power ÷ shaft power), but it is the standard way to estimate real pitch speed.

What is tip speed and why does it matter?

Tip speed is how fast the outer edge of the propeller moves through the air. When tip speed approaches the speed of sound (Mach 1, ~343 m/s), efficiency drops dramatically and noise increases. Keep tip speed below Mach 0.7 for best results.

How do I choose between pitch and diameter?

Larger diameter provides more thrust at lower speeds (better for takeoff and climbing). Higher pitch provides more speed but requires more power. For slow flyers and trainers, use larger diameter with lower pitch. For speed models, use smaller diameter with higher pitch.

ModelCalcs

Propeller Pitch Speed Calculator — Theoretical Max Speed

Calculate theoretical max speed from propeller diameter, pitch and RPM.

Propeller Diameter

First number on the prop, e.g. 10 in a 10×6 — sets tip speed

Propeller Pitch

Second number on the prop, e.g. 6 in a 10×6 — drives forward speed

Motor RPM

Prop RPM at full throttle (Kv × volts, less gearing/load)

UnitsInches for most RC props; mm for metric sizing

How We Calculate This

This calculator determines theoretical maximum airspeed from propeller pitch and RPM, then adjusts for real-world slip.

How it works

Theoretical speed (mph) = pitch (in) × RPM × 60 ÷ 63360, where 63360 is inches per mile and 60 is minutes per hour. This is the no-slip speed — the distance the prop would screw forward through solid air. The adjusted speed multiplies by the (1 − slip) factor (default 75%, i.e. ~25% slip) because a real prop always advances less than its geometric pitch. Tip speed = π × diameter × RPM, converted to mph and to Mach against 343 m/s (speed of sound at ~20°C sea level) to flag transonic tip losses.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always verify quantities before purchasing materials.