Minimum Plumbing Fixture Requirements by Occupancy (IPC Table 403.1)

Direct answer

Under the 2021 International Plumbing Code, Section 403.1 requires plumbing fixtures in the minimum number shown in Table 403.1, based on the actual use of the space and the occupant load determined by the International Building Code. Section 403.1.1 divides that occupant load in half for each sex, applies each fixture ratio and rounds every fraction up; where one set of toilet rooms serves several occupancies, the fractions are summed before rounding. Typical ratios are 1 water closet per 25 occupants for the first 50 and 1 per 50 after that in a Group B office, 1 per 75 in a restaurant, 1 per 40 in a bar, 1 per 50 in a school and 1 per 500 in a retail store. Section 403.2 requires separate facilities for each sex, except in dwelling and sleeping units, spaces with 15 or fewer occupants, mercantile uses of 100 or fewer, business uses of 25 or fewer, single-user rooms and all-gender rooms with enclosed water closet compartments.

Content and cited inputs reviewed by Harth team · Published 2026-10-27 · Updated 2026-10-27.

What are the key takeaways?

• Occupant split: Half the occupant load per sex, fractions rounded up
• Office (Group B) water closets: 1 per 25 for the first 50, then 1 per 50
• Restaurant water closets: 1 per 75 for each sex
• Single shared facility: Total occupant load of 15 or fewer

How is the minimum number of plumbing fixtures calculated?

The International Plumbing Code (IPC) sets plumbing fixture counts in Section 403. The method in the 2021 edition has five steps, and each one changes the answer if it is skipped.

1. Find the occupant load. IPC Section 403.1 takes the number of occupants from the International Building Code, so the count starts with the Chapter 10 occupant load calculation, not a separate plumbing number.
2. Pick the row by actual use. Table 403.1 is applied "based on the actual use of the building or space". A use the table does not list is considered individually by the code official.
3. Split by sex. Section 403.1.1 divides the total occupant load in half. A different split is allowed only where approved statistical data support it, and facilities designed for all genders are counted on 100 percent of the load.
4. Apply each ratio and round up. A ratio such as "1 per 75" means one fixture for every 75 persons or any fraction of 75 (footnote a). Every fractional result rounds up to the next whole fixture.
5. Sum fractions across occupancies. Where one set of toilet rooms serves more than one occupancy, the fractions for each occupancy are added first and rounded once at the end.

Water closets and lavatories have separate male and female columns in Table 403.1. The drinking fountain, bathtub or shower and service sink columns are not split by sex and are normally counted on the total occupant load; confirm that reading with the code official where a fraction decides the count.

Worked example: a 160-seat restaurant

A 2,400-square-foot dining room with tables and chairs has an occupant load of 160 at the IBC Table 1004.5 factor of 15 square feet net per occupant. Splitting it gives 80 men and 80 women.

In the men's room, Section 424.2 lets urinals replace not more than 67 percent of the required water closets in an assembly occupancy. Sixty-seven percent of 2 is 1.34, so one urinal may replace one water closet, leaving one water closet and one urinal. Footnote d adds any seasonal outdoor seating to the occupant load before the calculation.

Worked example: shared toilet rooms for two occupancies

A small building has a 60-occupant Group B office and a 120-occupant Group M shop sharing one pair of toilet rooms. Per sex that is 30 office occupants and 60 retail occupants.

Rounding each occupancy separately would have produced three water closets and two lavatories per sex. Summing first, as Section 403.1.1 requires, gives two and one. Drinking fountains on the total load are 60 / 100 + 120 / 1,000 = 0.72, so one is required, and one service sink serves the building.

When are separate men's and women's facilities not required?

Section 403.2 requires separate facilities for each sex wherever fixtures are required, with six exceptions in the 2021 IPC:

• dwelling units and sleeping units;
• structures or tenant spaces with a total occupant load, employees and customers combined, of 15 or fewer;
• mercantile occupancies with a maximum occupant load of 100 or fewer;
• business occupancies with a maximum occupant load of 25 or fewer;
• single-user toilet rooms provided under Section 403.1.2, which must be identified as available to all persons regardless of sex;
• multiple-user rooms designed for all sexes, where each water closet is in a compartment with walls or partitions and a door (Section 405.3.4) and urinals are in stalls or a visually separated area.

Section 403.2.1 also allows two family or assisted-use toilet rooms to serve as the required separate facilities where each sex would otherwise need only one water closet.

Where must the toilet rooms be, and who must be able to use them?

Section 403.3 requires toilet facilities for employees and, in buildings intended for public use, for customers, patrons and visitors. Parking garages without attendants, and quick-transaction tenants such as takeout counters with a public area of 300 square feet or less, are exempt from the public facility requirement. The route to public toilets cannot pass through kitchens, storage rooms or closets (403.3.1), and a toilet room cannot open directly into a room where food is prepared for the public (403.3.2). Outside malls, required facilities must be within one story above or below and a 500-foot path of travel (403.3.3). A toilet room for multiple occupants cannot have an egress door lockable from inside (403.3.6), and pay toilets count only in excess of the minimum (403.3.5).

What does the IRC require in a dwelling?

One- and two-family dwellings built under the International Residential Code follow IRC Section R306 rather than Table 403.1. Every dwelling unit needs a water closet, a lavatory and a bathtub or shower (R306.1), and every kitchen area needs a sink (R306.2). Kitchen sinks, lavatories, bathtubs, showers, bidets, laundry tubs and washing machine outlets need hot and cold water (R306.4). IRC Section P2705.1 sets the same layout clearances the IPC uses in Section 405.3.1: 15 inches from a water closet, lavatory or bidet centerline to a side wall or partition, 30 inches center to center between adjacent fixtures, and 21 inches of clear space in front.

IPC 2021 Table 403.1 minimum fixture ratios by occupancy

Ratios are reproduced from Table 403.1 of the 2021 International Plumbing Code. "1 per 75" means one fixture for each 75 occupants or fraction of 75. Where one value is shown for water closets or lavatories it applies to each sex. The IBC group column is an editorial cross-reference, not part of the table. Typical model-code values; verify against the AHJ-adopted edition and local amendments.

Table footnotes that change the count: employee toilets in prisons, detention centers and care facilities are separate from those for inmates or care recipients (b); one single-occupant toilet room may serve two adjacent patient sleeping units (c); seasonal outdoor seating counts toward the occupant load (d); outdoor public swimming pools follow Section 609 of the International Swimming Pool and Spa Code (f).

Rules that modify the Table 403.1 count

Where can you explore related guidance?

• Explore all design standards guidance
• ADA Restroom Dimensions & Clearances (Typical Minimums)
• IBC Occupancy Classifications: Groups A, B, E, F, H, I, M, R, S & U
• Traps, Interceptors and Separators: IPC Chapter 10 Requirements
• Plumbing Fixture Count Calculator: IBC Table 2902.1 Method
• Occupant Load Calculator: IBC Method, Factors and Worked Example
• Plumbing Fixture: Building Code Definition

Sources and method

Fixture ratios, calculation rules and exceptions are taken from the 2021 International Plumbing Code, Chapter 4, Fixtures, Faucets and Fixture Fittings (Table 403.1 and Sections 403, 405, 410, 419 and 424). Dwelling requirements come from 2021 International Residential Code Chapter 3 (Section R306) and Chapter 27, Plumbing Fixtures (Section P2705). The restaurant occupant load uses the IBC 2021 Table 1004.5 factor for unconcentrated assembly. Section numbering follows the 2021 editions; these are typical model-code values, so verify every ratio and exception against the edition adopted by the authority having jurisdiction, any state plumbing code (some states adopt the Uniform Plumbing Code instead) and local amendments.

Source links

• codes.iccsafe.org

• codes.iccsafe.org

• codes.iccsafe.org