Prop Pitch Calculator

What Is Propeller Pitch?

Propeller pitch is the theoretical distance a propeller would move through a solid medium in one revolution. A 16-inch pitch prop would advance 16 inches per turn if there were no slip in water.

Prop Pitch Formula

$$\text{Pitch} = \frac{\text{speed} \times \text{gear ratio} \times C}{\text{rpm} \times (1 - \text{slip})}$$

The constant $C$ depends on speed units: 1056 for mph, 656 for kph, and 1215.2 for knots. Gear ratio is engine revolutions per propeller revolution. Slip is entered as a decimal fraction of speed lost to water.

Choosing the Right Pitch

Higher pitch increases top speed but reduces low-end acceleration. Lower pitch improves hole shot and load carrying. Match pitch so the engine reaches its rated RPM at wide open throttle.

Related tool: Prop Slip Calculator.

Frequently Asked Questions

What is a typical prop slip value?

At wide open throttle, slip is often 10% to 20%. Lower slip means the prop is converting more rotation into forward motion.

What does gear ratio mean?

Gear ratio is how many engine crankshaft turns produce one propeller revolution. A 2:1 ratio means the engine spins twice per prop turn.

Can I calculate speed from pitch?

Yes. Rearrange the formula: speed equals pitch times rpm times (1 minus slip) divided by gear ratio and C.

Why is pitch measured in inches?

Marine propellers are sized in inches in the US market. The formula constants convert speed units to inches per minute.

Does diameter affect pitch choice?

Yes. Larger diameter props often use lower pitch. Diameter and pitch are both stamped on the propeller hub.

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What Is Propeller Pitch?

Prop Pitch Formula

Choosing the Right Pitch

Frequently Asked Questions

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