Portsmouth Yardstick (D-PN)

Who Owns It

United States Sailing Association

Why Did It Start

Originally introduced in Britain in the 1940’s, the Dixie Inland Yacht Racing Association (DIYRA) adapted the PY system in the 1960’s to develop the Dixie-Portsmouth Number (D-PN) system. Oversight of the new system was ultimately transferred to US Sailing, then United States Yacht Racing Union, in 1973. It is primarily used for rating smaller boats, including catamarans.

How It Works

The rating assessment relies exclusively on statistical analysis of national race results. Race results are plotted against Measured Ratings- a formulation of basic parameters such as waterline length, sail area, and displacement- to obtain a correlation between performance and MR for various wind speeds. Certain allowances are also available to account for common boat modifications. Conversion recommendations for IOR, MORC, and PHRF ratings are available as well. Ratings are reported as Time-on-Time Correction Factors. More details are highlighted in the Portsmouth Yardstick Handbook.

Who Uses It

Popularly used to rate centerboard boats, smaller keelboats, and multihulls, Portsmouth Yardstick is often used for local fleet races around the country.

Where We Fit In

US Sailing Portsmouth Numbers Committee is charged with the maintenance of the rule including compiling race results submitted by supporting clubs and developing the tables of modification factors for all classes.

What’s Required

Certain basic boat parameters must be known to calculate a boat’s MR and may be declared by the owner supported by manufacturer or designer specifications.


The Portsmouth Yardstick relies on accurate reports of race results from clubs like yours. Become a Supporting Club today!


Access to all Portsmouth Yardstick handicapping tables is free to all sailors.


The new Portsmouth Yardstick racing platform has launched! As a new benefit for member organizations, US Sailing has partnered with the Royal Yachting Association to create a more robust platform for Portsmouth Yardstick Racing using the PYOnline platform.

The accuracy of the ratings is one of the key advantages. The ratings will become more accurate over time, ensuring that competition stays fresh on the water. This means no one boat or class is guaranteed a win or loss based upon ratings alone. Each club will have ratings that are based on their local conditions. US Sailing will update the national ratings for a given class on an annual basis, based upon the ratings used by the individual clubs. Portsmouth Yardstick racing becomes better, more robust and more fun with more clubs and sailors participating.

Other Resources