Handicapping allows vessels to compete across classes, and also allows vessels and crews to compete based on performance and equipment on an equal basis, by adjusting the race outcome data, to declare a handicap (adjusted) winner as distinct from a line honours (first over the finish line) winner.
The adoption of the British Thames Measurement by the Yacht Club de France in 1870 may mark the beginning of international rating rules.
The Universal Rule determined a yacht's eligibility to race in the America's Cup from 1914 to 1937 and for this the J-class was chosen.
Additionally, the IOR identified features which were dangerous, or it couldn't fairly rate, and penalized or prohibited them.
The measurements and penalties were used to compute the handicap number, called an IOR rating, in feet.
While some yachts race at club level under ORC or IRC in more or less their original form, others had major surgery to make them competitive within the new rules.
[2] While most other rules do not take past performance into account, PHRF differentiates itself by allowing skippers to request handicap reductions after a series of poor racing results.
[3] IRC is a system managed by the Royal Ocean Racing Club (RORC) in the United Kingdom through their dedicated Rating Office,[4] and the Union Nationale pour la Course au Large (UNCL) in France.
The aim is to cancel out the inherent advantages and disadvantages of each class of boats, so that results reflect crew skill rather than equipment superiority.
In some countries a Performance Handicap Racing Fleet (PHRF) may be used to rate trailer sailers, such as in NZ and in the USA and Canada.
Class Based Handicap (CBH) measurement system is used, for example, for trailer sailers, such as in Australia and also in New Zealand.
In Australia, the CBH system is a nationally governed handicap designed to assess the potential speed of the boat.