How Many Porta Potties Do I Need? A Wisconsin Sizing Guide

Wisconsin special event restroom requirements

Wisconsin has no statewide portable restroom ratio for public events. Requirements are set municipality by municipality, and only a minority of cities publish a binding numeric table. Where no ordinance table exists, organizers and suppliers size orders using Portable Sanitation Association International guidance.

Source: Individual Wisconsin municipalities; Portable Sanitation Association International, Municipal special event ordinances; PSAI event guidance. View the primary source. Verified August 2026.

The two starting numbers

Events start at one standard unit per 50 guests over 8 hours. Construction sites start at one unit per 20 workers on site at any one time.

Everything else is an adjustment to one of those two figures. The mistake that produces almost every undersized order is stopping at the starting number and skipping the adjustments below.

Step by step: sizing an event order

Work through five adjustments in order: peak attendance, duration, alcohol, food, and accessibility.

First, use peak simultaneous attendance rather than total gate count, because that is the figure municipal tables key on. Second, extend for duration, since events past 8 hours need more units or a mid-event service visit. Third, add 10 to 20 percent if alcohol is served. Fourth, add hand-wash stations if food is served, at one per two restrooms as a safe default. Fifth, include at least one ADA unit, and one per 20 standard units at scale.

Step by step: sizing a construction order

Size on peak simultaneous crew count, apply the OSHA tier, then check the result against tank capacity.

The capacity check is the step contractors skip. A 60 to 70 gallon tank serves roughly a 10-person crew for a week. Divide your peak crew by 10 to get the number of unit-weeks of capacity you consume per week, then either add units or add service visits until supply meets that figure. A site at the bare OSHA minimum almost always needs twice-weekly service rather than weekly.

Wisconsin-specific adjustments

Two local factors change the answer here: winter servicing and peak-season inventory scarcity.

From December through March, antifreeze charging is added to every service visit and hand-wash stations are generally pulled and replaced with sanitizer. Between Memorial Day and Labor Day, and especially during EAA AirVenture week in late July, regional inventory tightens enough that the number you can actually get may be lower than the number you want. Book summer weekend events 2 to 4 weeks out and restroom trailers 4 to 8 weeks out.

Worked examples

Three common Wisconsin scenarios, sized end to end.

A 150-guest outdoor wedding reception running 6 hours with a bar: 4 standard units at the tighter wedding ratio, or one 2-station restroom trailer plus one ADA unit, with 2 hand-wash stations. A 25-worker commercial job site: OSHA requires 1 toilet seat and 1 urinal, but tank capacity for 25 workers means 2 to 3 units with weekly service is the realistic placement. A 3,000-person community festival running 6 hours in Waukesha: the city table requires 12 toilets, plus 2 hand-wash stations at the local 1-per-6 rule if food is served.

Key points

• Waukesha counts attendees at any given time, not aggregate attendance across the day. An event that draws 6,000 people total but never holds more than 1,500 at once is sized on the 1,500 figure.
• The required count may be satisfied with permanent restrooms, portable toilets, or any combination, and all toilet facilities must comply with ADA accessibility requirements.
• If permanent private restrooms are used to meet the requirement, Waukesha requires a written agreement from the owner making them free to the public throughout the event, placement within 200 feet of the event boundary, and clear directional signage.
• Where food is consumed and any part of the requirement is met with portable toilets, Waukesha requires at least 1 portable hand-washing station for every 6 portable toilets.
• Most Wisconsin municipalities do not publish a table at all and instead require adequate facilities at the organizer's expense, leaving the number to the organizer and their supplier.

PSAI sizing guidance

Adjustments that change the number

• Add 10 to 20 percent more units when alcohol is served, which is the most common cause of an undersized order.
• Provide one hand-wash station for every two portable restrooms.
• Provide at least one ADA-accessible unit at every event, and one accessible unit per 20 standard units at scale.
• Events longer than 8 hours need either additional units or mid-event servicing.
• Multi-day events running Friday through Sunday should schedule overnight servicing between operating days.
• Weddings and events skewing toward female attendance are commonly sized at 1 unit per 35 to 50 guests rather than the 1 per 50 baseline.

Frequently asked