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.

Other Resources