46 CFR § 115.113 - Passengers permitted.
(b) The maximum number of passengers permitted on any vessel may be the greatest number permitted by the length of rail criterion, deck area criterion, or fixed seating criterion described in this paragraph or a combination of these criteria as allowed by paragraph (c) of this section.
(1) Length of rail criterion. One passenger may be permitted for each 760 millimeters (30 inches) of rail space available to the passengers at the periphery of each deck. The following rail space may not be used in determining the maximum number of passengers permitted:
(i) Rail space in congested areas unsafe for passengers, such as near anchor handling equipment or line handling gear, in the way of sail booms, running rigging, or paddle wheels, or along pulpits;
(ii) Rail space on stairways; and
(2) Deck area criterion. One passenger may be permitted for each 0.9 square meters (10 square feet) of deck area available for the passengers' use. In computing such deck area, the areas occupied by the following must be excluded:
(i) Areas for which the number of persons permitted is determined using the fixed seating criteria;
(ii) Obstructions, including stairway and elevator enclosures, elevated stages, bars, and cashier stands, but not including slot machines, tables, or other room furnishings;
(iii) Toilets and washrooms;
(iv) Spaces occupied by and necessary for handling lifesaving equipment, anchor handling equipment or line handling gear, or in the way of sail booms or running rigging;
(vi) Interior passageways less than 840 millimeters (34 inches) wide and passageways on open deck, less than 710 millimeters (28 inches) wide;
(vii) Bow pulpits, swimming platforms and areas that do not have a solid deck, such as netting on multi-hull vessels;
(viii) Deck areas in way of paddle wheels; and
(ix) Aisle area provided in accordance with § 116.820(d) of this chapter.
(3) Fixed seating criterion. One passenger may be permitted for each 455 millimeter (18 inches) of width of fixed seating provided by § 116.820 of this chapter. Each sleeping berth in overnight accommodation spaces shall be counted as only one seat.
(c) Different passenger capacity criteria may be used on each deck of a vessel and added together to determine the total passenger capacity of that vessel. Where seats are provided on part of a deck and not on another, the number of passengers permitted on a vessel may be the sum of the number permitted by the seating criterion for the space having seats and the number permitted by the deck area criterion for the space having no seats. The length of rail criterion may not be combined with either the deck area criterion or the fixed seating criterion when determining the maximum number of passengers permitted on an individual deck.