There are no regulation for the rating of the rudder area and very often crude empirical methods such as percentage of the underwater lateral area are used.
This gives a rudder blade area of approximately 1.5% of the underwater lateral area LxT for ships of usual width; for the unusually broad ships (large mass, large windage area, low yaw stability) a somewhat larger value is given. This corresponds to typical rudder designs and can serve as a starting point for further analyses.
