How Many Bathrooms Does a Commercial Building Need?

Modern Northwest Design and Build Team · Published August 3, 2026

Under the code used in Oregon, an office needs about one toilet per 25 occupants for the first 50 people, then one per 50 after that. A retail store needs one per 500, and a restaurant one per 75. And if your space is small, one single-user restroom is often all the code asks for: in Oregon that covers most spaces up to 30 occupants, and offices up to 50. Those numbers settle the question for most build-outs. The rest of this guide covers where they come from, the ADA sizing rules, and the Oregon-specific details that surprise people.

From Table 2902.1 of the Oregon Structural Specialty Code and its separate-facilities exceptions (full sources below). Ratios apply to the occupant load the building department calculates, not your headcount.

We build tenant improvements and commercial spaces across Portland and Southwest Washington, and the restroom count is one of the first things a building department checks in plan review. Here is how the math actually works, so you can sanity-check a space before you sign a lease for it.

How the count is calculated

The code does not care how many people work for you. It cares about occupant load: the number the building department assigns your space based on its floor area and use. A 3,000 square foot office and a 3,000 square foot restaurant hold very different occupant loads, which is why the restaurant needs more fixtures even if fewer people are ever inside.

The ratios are then applied to that occupant load, split between the sexes, and fractions always round up. Worked example: a 100-occupant office splits to 50 per sex, and at 1 per 25 that means 2 toilets each, so 4 total. The same 100 occupants in a retail store, at 1 per 500, need just 1 per sex, and retail at that size qualifies for an exception anyway, which is the next section.

When is one restroom enough?

This is the question most small tenants actually have, and Oregon's answer is more generous than people expect:

• Most spaces up to 30 occupants: one single-user restroom is permitted.
• Offices up to 50 occupants: one single-user restroom is permitted.
• Retail up to 100 occupants: separate men's and women's rooms are not required.

That single-user room still has to meet ADA dimensions, and in Oregon it must be signed for use by everyone, which is covered below. For a small office or shop build-out, this exception often saves a full second restroom: real plumbing, real square footage, real money.

What size does the restroom need to be?

Accessibility sizing is where restrooms fail plan review. The numbers that govern the room, straight from the ADA Standards:

• Turning space: a 60 inch diameter circle (or T-shaped equivalent) clear inside the room.
• Accessible toilet compartment: 60 inches wide minimum by 56 inches deep for a wall-mounted toilet, 59 inches deep for floor-mounted.
• Toilet centerline: 16 to 18 inches from the side wall. This one is unforgiving; an inch off fails inspection.
• Grab bars: a 36 inch minimum bar on the rear wall and a 42 inch minimum bar on the side wall, mounted 33 to 36 inches high.
• Lavatory clear floor space: 30 by 48 inches for a forward approach.
• Toilet seat height: 17 to 19 inches to the top of the seat.

The code sets minimum clearances, not a room size, but once the turning circle, door swing, and fixtures are all accounted for, the single-user restrooms we build usually end up somewhere around 7 by 8 feet. Trying to squeeze the room smaller than the clearances allow is the most common redline we see on tenant drawings.

Employees have their own math: OSHA

The building code counts occupants; OSHA counts employees, and both apply to you. Under OSHA's sanitation standard (29 CFR 1910.141), a workplace needs 1 toilet for up to 15 employees, 2 for 16 to 35, 3 for 36 to 55, 4 for 56 to 80, and roughly one more per 40 employees beyond that. For most build-outs the building-code number is the larger of the two, so it governs, but a warehouse with a big crew and a tiny public occupant load can flip that.

The Oregon rules people don't see coming

Two state-specific rules matter on top of the national tables:

All-user signage is the law here. Since House Bill 3313 in 2017, every single-occupancy restroom in an Oregon place of public accommodation must carry gender-neutral signage: "Restroom" or "All-Gender Restroom," not "Men" or "Women." The state building code says the same thing from the construction side: single-user toilet rooms are identified as available to all persons regardless of sex. If your build-out includes single-user rooms, the signage package is part of passing final, not an afterthought.

Medical and dental spaces run richer. Clinics add patient restrooms and staff facilities beyond the base table, and the layout interacts with everything else in a clinical build-out, from ADA clearances to plumbing runs. If that is your project, count restrooms early, because clinic plumbing walls are the most expensive ones to move.

Why this gets settled at plan review, not during construction

The occupant load, the fixture count, and the accessibility dimensions all get checked when your permit application goes through plan review. That is the cheap moment to fix them. Adding a restroom after framing means new supply and waste lines through finished work, and it is one of the most expensive mid-build changes there is. Who files that permit application, and how review works in Portland, Multnomah County, Washington County, and Vancouver WA, is its own topic: see our guide to who pulls the permit.

If you are budgeting a build-out in a leased space, restrooms are also one of the line items your tenant improvement allowance has to cover, so a space that needs an extra restroom is genuinely more expensive to take than one that does not.

Looking at a space right now? Send us the square footage and use and we will tell you what restroom count plan review will expect before you commit to the lease.

Frequently asked questions

The bottom line

Restroom count comes down to three things: your occupancy type, the occupant load the building department assigns, and whether you fit inside the single-user exceptions. Check those against any space before you lease it, because the difference between one restroom and three is real money in a build-out budget.

Modern Northwest builds tenant improvements and commercial projects across Portland and SW Washington, and we handle the occupant-load math, ADA layout, and permitting as part of every job. Reach out for a free walkthrough.