How Many Porta Potties Do I Need?

How many porta potties per guest?

The figure most event planners start from is one porta potty for every 50 guests over about four hours. It's a starting point, not the answer. It assumes a fairly normal crowd, no bar, and people spread out over the afternoon.

From there you adjust up. You'll rarely adjust down.

What increases the number you need?

Each of these on its own is a reason to add units:

• ✓Longer events. A six- or eight-hour event needs more than a four-hour one with the same guest list. Units fill up and lines get longer as the day goes on.
• ✓Alcohol. People who are drinking use the restroom more often. If there's a bar, plan for noticeably more capacity than the headcount alone suggests.
• ✓Everyone going at once. Halftime, the end of a race, the break between bands. Crowds move together, and the line forms at those moments, not on average.
• ✓Food and drink stalls. Lots of drinks and food usually means more trips.
• ✓Hot weather. People drink more water, and units need servicing more often.
• ✓A spread-out site. If guests have a long walk, split the units into two or more groups. That usually means rounding up.

Worked examples

These use common planning figures. Your permit, venue or crowd may call for more.

• ✓Backyard graduation party, 60 guests, 4 hours, no bar: 2 standard units. One would work on paper, but 60 is over the 50-guest mark and two avoids a line.
• ✓Wedding, 150 guests, 6 hours, open bar: 5 units is a sensible starting point. Consider deluxe units, and add an accessible unit for older guests.
• ✓Community festival, 800 people across a whole day, beer tent: work it out per session rather than for the whole day, split units between the entrance and the food area, add accessible units, and check what your permit requires.
• ✓5K fun run, 300 runners: the crowd is heaviest right before the start and right after the finish, so put most units near the start line and size for that rush.

How is a job site different?

On a construction site you're not planning for a rush. You're planning for the same crew using the units every day, all week.

A common rule of thumb is one unit for about 10 workers on a 40-hour week with weekly service. Bigger crews, longer shifts or hot weather usually mean more units, more frequent service, or both.

There's also a legal minimum. OSHA's construction sanitation rule, 29 CFR 1926.51, requires at least one toilet for 20 or fewer workers and more as the crew grows. The rule of thumb above is about keeping units usable, and it's usually more generous than the legal minimum.

Do you need accessible units and handwashing?

If your event is open to the public, plan on at least one ADA accessible unit. A common figure is about one for every 20 standard units, and your permit may specify the number.

If food is served, you'll almost certainly need handwashing stations, both near the food and near the restrooms.