Capacity plates are not required on vessels over 20 feet in length. The following is an excerpt taken from SAILING FUNDAMENTALS (The Official Learn-To-Sail Manual of the American Sailing Association and the United States Coast Guard Auxiliary) by Gary Dobson, page 28 "For home built or other boats not required to have a capacity plate the following formula can be used to estimate the maximun number of persons who can safely ride in the boat on a calm day. Multiple the length (in feet) by the width (in feet) and divide this by 15. Round the result down to the nearest whole number. For example, a boat with a length of 20 feet and a beam of 6 feet could safely carry (20 X 6)/15=8 person on a calm day. This formula assumes the average weight of a person is 150 pounds - adjustments should be made if this assumption is incorrect. Note that the length of the boat is measured along a straight line from its bow to its stern. The length does not include bowsprits nor it include rudders, brackets, outboard motors, diving platforms or other attachments."
Fair Winds,
Ben & Di