The Offshore Racing Congress Rule is a system of handicapping sailboats for the purpose of racing that is being developed and promoted to replace the IRC currently in general use (as of 2008). It is managed by the Offshore Racing Congress (ORC) and is usually referred to in the sailing community simply as "ORC".
ORC is an enhanced version of the earlier IMS handicapping system that was the dominant system used globally from the early 1990s to the early 2000s.
The ORC rule uses essentially the same concepts as the earlier IMS system but with a much more sophisticated velocity prediction program performing the handicapping calculations than was available in the IMS era. This improved program is designed to eliminate the problems that led to IMS falling out of favour with yacht clubs in the early 2000s.
IMS is (as of 2008) gaining support among the premium ocean racing clubs around the world[1][2] as it is an open system, where all the details of the handicapping formula are available to designers and boat owners. This allows a greater degree of certainty when designing boats than closed, secret formulas such as IRC allow for. Also, being open, every individual yacht club can perform the handicapping calculations and issue handicap certificates for the yachts in their own fleets. This eliminates the bottle necks and delays encountered when waiting for certificates to be issued by a single global authority, such as has been experienced with the IRC rule.
To encourage the growth of the rule, two versions have been developed. The ORC-International rule is the full complexity, highly developed version for top level championship racing. An ORC-Club rule has also been developed, which is a simplified version more easily used by smaller clubs who have less resources.