Porta potty calculator: how many portable toilets do you need?

How the event formula works

Whether you call it a porta potty, a portable toilet or a portable bathroom, the sizing is the same. The calculator above runs on four rules. None of them is a law; they are the industry sizing conventions that keep lines under 5 minutes at a 4-hour event, made slightly conservative because a short line is cheaper than an angry crowd.

1. Base rate: 1 unit per 50 guests, rounded up. 100 guests need 2 units; 101 guests need 3.
2. Duration: +50% of the base for every extra 4-hour block. The formula divides the hours by 4 and rounds up to get blocks, then multiplies the base by 1 + 0.5 × (blocks − 1). A 5-hour event counts as 2 blocks, so 100 guests at 5 hours need 3 units, not 2.
3. Alcohol: ×1.2, rounded up. A bar roughly doubles restroom visits per hour; 20% is the conventional allowance.
4. ADA at 5%, minimum 1, replacing one standard unit. When the public is invited, California requires 5% of clustered portable restrooms (minimum 1) to be wheelchair accessible under CBC 11B-213 and the 2010 ADA Standards. The calculator takes that ADA unit out of the total rather than adding it, so the count stays honest.

A handwash station is then added at 1 per 4 toilets, rounded up, minimum 1. County environmental health asks for handwashing in the sanitation plan whenever food is served, and a handwash station at the catering line usually covers the vendors too.

Worked examples: events of 4 hours

Read the 50-guest row carefully: 1 unit without alcohol means the single unit is the ADA unit, which is the right call for a public gathering anyway. With a bar, the 50-guest party gets 1 standard unit and 1 ADA unit. The 1,000-guest row crosses the second ADA threshold only with alcohol, because 5% of 24 is 1.2, which rounds up to 2.

Each standard portable toilet in the table is $195 for an event of up to 3 days, each ADA unit $325 and each handwash station $99, delivered, stocked and picked up within 25 miles of Hayward. The portable restrooms near me page shows what the 25-mile rule does to the price in your city.

Longer events, weddings and multi-day festivals

Duration is the variable most people skip. The table holds 100 guests constant and changes the hours.

For a 5-hour seated wedding, our wedding sizing guide uses the lighter 1-per-75 rule of thumb, because seated guests with a timed dinner visit less often than a standing crowd. A 150-guest wedding with a bar sizes to 3 units by that rule and to 6 by the calculator's general-event formula; the honest answer is that at 150 guests most couples stop comparing single units and book a 2-stall restroom trailer at $2,495 per weekend. The restroom trailers hub matches trailer size to guest count.

Multi-day festivals size by the busiest day, then add a mid-event pump-out at $125 per visit for each day after the first. A 2,000-person, 8-hour festival day without alcohol needs 60 units; the events page covers layout, attendants and the county sanitation plan.

How the construction formula works

Construction sizing is not a convention; it is Cal/OSHA. Two sections of Title 8 set the ratios, and the calculator applies them exactly.

• 8 CCR §1526, toilets. One toilet per 20 employees or fraction thereof, per sex. Crews under 5 may share one lockable single-user unit, and up to half the men's fixtures may be urinals. The calculator rounds the headcount up to the next 20: 21 workers need 2 toilets.
• 8 CCR §1527, handwashing. One washing facility per 20 employees, next to the toilets, with soap and single-use towels. Hand sanitizer does not count. The ratio is the same as the toilet ratio, so every standard unit gets a handwash station.
• AB 521, the designated women's unit. AB 521 directs Cal/OSHA to require at least one single-user toilet per job site designated for employees who identify as female or nonbinary. The calculator adds a women's unit, with a keyed lock, signage and a sanitary bin, for every crew of 5 or more. Verify the current adoption status with the Occupational Safety and Health Standards Board; the AB 521 guide tracks it.
• No ADA unit on worker-only sites. ADA 2010 Standards §203.2 exempts construction-worker-only toilets. The calculator adds none; a sales office or public tour changes that.

Worked examples: construction crews

A crew of 5 and a crew of 15 get the same 3 units because both fall inside the first block of 20. That 3-unit set, a standard unit, a women's unit and a handwash station, is the Cal/OSHA compliance pack at $479 per month, $38 less than the three items at $189, $199 and $129. Our Cal/OSHA guide has the inspector's view of the same numbers, and the construction toilet requirements guide covers the federal baseline.

What it costs

The calculator prices its result by ZIP, but the arithmetic is simple enough to show. Event prices are per event of up to 3 days; construction prices are per 28 days and include one service visit per week.

Beyond 25 miles from Hayward, add $3.50 per mile each way on the extra miles: San Jose at 28 miles adds about $11 per trip, San Francisco at 30 miles about $18. Every number above is the price on the invoice, with delivery, pickup, consumables and tax included; the pricing page lists the add-ons, such as a second weekly service at $45 per unit for crews above 10 workers per toilet.

Price your exact count for any Bay Area ZIP in 30 seconds: Instant price · or call (650) 977-2883.

When a trailer replaces the cluster

Past 150 guests, the question changes from "how many porta potties" to "cluster or trailer". A 300-guest, 4-hour reception with a bar sizes to 8 single units plus 2 handwash stations; built from luxury flushing porta potties with the ADA unit, that cluster is $2,588. A 4-stall luxury restroom trailer at $3,295 per weekend serves the same 300 guests with porcelain flush toilets, running water and climate control for the extra $707. For public events, the trailer still needs the 5% accessible unit beside it, or you book the ADA+2 trailer at $3,495. For film basecamps and multi-day builds, the shower trailer at $3,495 per weekend adds 8 private shower stalls to the restroom count.