IPC 403.1 · Minimum plumbing fixtures

How to calculate minimum plumbing fixtures by occupancy

Occupant load, the per-sex split, tiered ratios, rounding, mixed occupancies, and when separate restrooms are not required — with a worked example and a free link to the official table.

Need the actual table? Read IPC Table 403.1 free at codes.iccsafe.org →

How to use Table 403.1, step by step

Step	What you do	Watch out for
1	Confirm the occupancy classification (A, B, E, F, I, M, R, S, etc.) and find its row in Table 403.1	Assembly occupancies are split into sub-rows (restaurants, theaters, worship, arenas) with very different ratios
2	Get the occupant load from the building code (IBC Chapter 10 occupant-load factors), not from the owner’s headcount	The plumbing count follows the same occupant load the architect used for egress
3	Split the occupant load in half, one half per sex (403.1.1)	Split first, then calculate — do not calculate on the total and divide the result
4	For each fixture type, apply the ratio in the row to each half. Where the row has tiers ("first X, then 1 per Y for the remainder"), work each tier separately	Round each fixture type up to the next whole fixture — fractions always round up
5	Drinking fountains and service sinks are figured on the total occupancy, not per sex	Water dispensers such as bottle fillers can replace part of the drinking-fountain requirement in some occupancies (410.4)
6	For mixed occupancies, total the fractional fixtures across occupancies before rounding (403.1.1)	Rounding each area separately over-counts fixtures
7	Check separate-facility rules and exceptions (403.2), employee vs. public access (403.3), and urinal substitution limits (424.2 in the 2021 IPC; 419.2 in older editions)	Single-user and family/assisted-use rooms can count toward the total (403.1.2)

Our own summary, not the code text. Read Table 403.1 free at codes.iccsafe.org (2021/2024 IPC) and verify against the edition and local amendments adopted by your AHJ.

Which rule answers the question?

Question on the job	Where to look	What it controls
How many of each fixture?	IPC Table 403.1 (mirrored in IBC Table 2902.1)	Ratios by occupancy row
How do I split and round?	IPC 403.1.1	Even split by sex, round up, total fractions for mixed use
Do single-user or family rooms count?	IPC 403.1.2	Counts toward the required total
Must men’s and women’s rooms be separate?	IPC 403.2 and its exceptions	Small tenants, some mercantile/business spaces, single-user rooms, and (2024) all-gender multiple-user rooms
Do customers get access?	IPC 403.3	Public access, travel distance, and floor-level limits
Can I swap water closets for urinals?	IPC 424.2 (2021; 419.2 in older editions)	Maximum substitution percentage by occupancy

Our own summary, not the code text. Read Table 403.1 free at codes.iccsafe.org (2021/2024 IPC) and verify against the edition and local amendments adopted by your AHJ.

Worked example — office (Group B), occupant load 120, water closets only

Input / step	Value	Source
Occupant load (from the architect’s code plan)	120	IBC Ch. 10
Occupants per sex	60	403.1.1 — split in half
Business water closet ratio	1 per 25 for the first 50, then 1 per 50 for the remainder	Table 403.1, Group B row
First tier: 50 ÷ 25	2.0	—
Second tier: (60 − 50) ÷ 50	0.2	—
Total per sex	2.2 → round up to 3	403.1.1
Result	3 water closets for each sex (6 total)	Repeat the same process for lavatories

Worked example value only. Read the full table free at codes.iccsafe.org; your AHJ’s amendments may change the ratios.

Worked example 2 — do I need separate rooms? 20-person business tenant

Input / step	Result	Source
Occupancy and total occupant load	Group B, 20 people	Code plan
Business exception threshold	Separate facilities not required at 25 or fewer	403.2 exception (2021 IPC)
Result	One single-user toilet room serving everyone can satisfy the separation rule — you still need the fixture count from Table 403.1	403.2, 403.1.2

Worked example value only. Exceptions differ by occupancy and edition — check the edition your AHJ enforces.

Common mistakes

Mistake	What to do instead
Using the owner’s employee headcount	Use the code occupant load from the egress analysis — it is usually higher
Calculating on the total and then halving the answer	Split the occupant load first, then apply the ratio to each half
Rounding down "0.2 of a toilet"	Every fraction rounds up to a whole fixture
Rounding each tenant area separately in a mixed-use building	Sum the fractions across occupancies first, then round once
Replacing most water closets with urinals	Urinal substitution is capped (424.2 in the 2021 IPC) — the cap differs by occupancy
Forgetting customers	Many occupancies must provide public toilet access within a travel-distance limit (403.3)

Our own summary, not the code text. Read Table 403.1 free at codes.iccsafe.org (2021/2024 IPC) and verify against the edition and local amendments adopted by your AHJ.

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Getting the restroom count right before the walls go up

Read Table 403.1 free on codes.iccsafe.org. ICC offers free read-only access to the International Plumbing Code (2021 and 2024 editions). This page explains how to use the table; it does not reproduce it.

The fixture count is one of the first plumbing numbers that gets locked in, and one of the most expensive to fix late: an extra water closet after framing means a new chase, new drain, and often a lost office. The count comes from the occupant load — the same number the architect used for egress — not from how many people the owner plans to hire.

The method. Split the occupant load in half, apply the row’s ratio to each half, and round every fraction up. Many rows are tiered — a tighter ratio for the first block of people and a looser one for everyone after — so work each tier separately and add them. In a mixed-use building, add up the fractional fixtures from each occupancy before you round.

Worked example. A 120-person office splits to 60 per sex. The business row calls for 1 water closet per 25 for the first 50 and 1 per 50 after that: 2.0 + 0.2 = 2.2, which rounds up to 3 water closets per sex. Run the lavatories the same way; drinking fountains and the service sink are figured on the whole building.

Separate facilities. Section 403.2 requires separate facilities by sex, then lists exceptions — dwelling units, very small tenants, and some smaller business and mercantile spaces — and lets single-user rooms serve everyone. The 2024 IPC added multiple-user all-gender rooms as an option, with the count based on the full occupant load. Western jurisdictions on the Uniform Plumbing Code (IAPMO) use UPC Table 422.1 instead; the ratios and occupant-load rules differ.

Once fixtures are counted, size the pipes that serve them: drainage fixture units and drain sizing, water supply pipe sizing, and vent sizing. Field PM keeps the code plan, RFIs, and inspection records with the job so the fixture count is settled before rough-in.

FAQ

How do I calculate the number of toilets required by code?+

Get the occupant load from the building code, split it in half by sex, find your occupancy row in IPC Table 403.1, apply the water-closet ratio to each half (working each tier separately), and round up. Drinking fountains and service sinks use the total occupant load. Read the table free at codes.iccsafe.org.

Is the IPC fixture table the same as IBC Table 2902.1?+

The IBC carries the same minimum-fixture requirements in Chapter 29 so building plan reviewers and plumbing inspectors work from matching numbers. If your jurisdiction amends one, check whether it amended the other.

When are separate men’s and women’s restrooms not required?+

IPC 403.2 has exceptions for dwelling and sleeping units, very small total occupant loads, and smaller mercantile and business spaces, and single-user rooms can serve all persons. The 2024 IPC added an option for multiple-user all-gender facilities. The thresholds differ by occupancy, so read 403.2 in your adopted edition.

What changed in the 2024 IPC fixture requirements?+

The headline change is a new path for multiple-user toilet facilities that serve all genders, with the fixture count figured on the full occupant load rather than half per sex, plus related signage language. Check your state’s adoption — many jurisdictions still enforce the 2018 or 2021 edition.

What about the Uniform Plumbing Code?+

Jurisdictions on the UPC (common in the western US) use UPC Table 422.1 and its own occupant-load rules, which differ from the IPC in ratios and in how occupant load is determined. Do not mix the two codes on one project; consult the UPC through IAPMO.

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