Prop setup calculator

PropSlip

Pitch / RPM / Gear / Speed

Calculated slip

--

Waiting
Prop RPM --
Theoretical --
in
:1
rpm

How to Use

1. Enter the prop pitch

Use the pitch stamped on the propeller, usually shown in inches.

2. Enter gear ratio

Use the lower-unit ratio as a number, such as 1.75 for 1.75:1.

3. Add RPM and GPS speed

Use engine RPM and actual GPS speed from the same run for the best estimate.

4. Read the slip result

Lower slip often indicates a more efficient setup, but hull, load, trim, water, and prop style all matter.

What is Propeller Slip?

Propeller slip is the gap between how far the propeller should advance in theory and how far the boat actually moves through the water. PropSlip helps compare setup changes, prop choices, and running conditions.

If the calculator returns a negative slip value, the inputs are probably outside normal conditions. Common causes are a data entry error, an inaccurate tach or GPS reading, or a boat running down-current or downwind and moving faster than the calculated theoretical maximum.

Slip percentage

Slip % = Theoretical speed - Actual speed Theoretical speed x 100

Privacy

Last updated

July 24, 2026.

On-device calculation

The calculator runs entirely in this page. Your pitch, ratio, RPM, and speed values are not sent anywhere.

Browser storage

PropSlip stores appearance and speed-unit preferences in this browser. These preferences stay on this device.

Data collection

The current site does not use cookies, analytics, advertising trackers, contact forms, or payment forms. A web host may process standard server logs, such as IP address and request time, to deliver and secure the site.

Data sharing

PropSlip does not sell personal information or share calculator inputs with third parties. Hosting providers may process technical request data needed to operate the site.

Updates

This notice may be updated as the site changes. It should be reviewed before adding analytics, contact forms, ads, payments, accounts, or mobile app data collection.

Children

PropSlip is not directed to children and does not knowingly collect personal information from children.

Accessibility

Current support

Visible labels, large touch targets, keyboard focus, live result updates, dark mode, and reduced-motion support are built in.

Target standard

PropSlip aims to support WCAG Level AA for the website and future mobile app releases.

Color safety

Results use text labels and numeric values so color is not the only signal.

Report a barrier

Email propslipsupport@gmail.com with the page, device, browser, and accessibility issue so it can be reviewed.

Terms & Disclaimer

Last updated

July 24, 2026.

Informational use

PropSlip provides estimates for setup planning and comparison. It is not a substitute for manufacturer specifications, professional marine advice, inspection, or safe boating judgment.

Accuracy

Results depend on the values you enter and simplify real-world conditions. Hull design, load, trim, water, altitude, propeller condition, and measurement error can all change actual performance.

Safety

Always operate within posted limits, manufacturer ratings, equipment ratings, local laws, and safe conditions. Do not use calculator output as the only basis for a propeller, engine, or operating decision.

No warranty

The calculator is provided as-is, without warranties of accuracy, availability, performance, or fitness for a particular purpose.

Use at your own risk

You are responsible for setup decisions, operation, inspection, maintenance, and safety. PropSlip is not liable for damage, injury, loss, or performance outcomes from using calculator results.

Ownership

The PropSlip name, design, text, and calculator implementation belong to the site owner unless otherwise noted.

Changes

These terms may be updated as the site changes. Continued use of the site means you accept the current terms shown here.

Contact

Support contact

Email propslipsupport@gmail.com for privacy, accessibility, and site-support questions.

Feedback

Use contact messages for calculator bugs, accessibility barriers, and formula questions. Do not send sensitive personal, financial, medical, or location information.

Settings

Appearance
Speed units

System follows your device appearance. Speed unit changes convert the visible speed value. Pitch always remains inches.