Sizing guide
How Many Porta Potties Do I Need? Event and Jobsite Sizing
A calculator, a table and the exact whole-unit steps behind them, so you order the right number instead of the biggest number.
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How many porta potties do I need for my event?
For a 4-hour event, plan 1 standard porta potty per 50 guests, rounded up. Add 1 unit per 100 guests (rounded down, minimum 1) when alcohol is served, add the same number for every 4 hours beyond the first 4, and make at least 5% of each cluster (minimum 1) wheelchair-accessible. A 150-guest, 5-hour wedding with a bar needs 5 units: 3 for headcount, 1 for time, 1 for alcohol, one of them accessible.
Sizing calculator
Method: Portable Sanitation Association International (PSAI) event guidance of roughly 1 unit per 50 people per 4 hours, applied in whole-unit steps. This is our recommendation for comfort, not a legal minimum. The accessible count follows the 2010 ADA Standards §213.2 (5% of each cluster, minimum 1).
| Guests | 4-hour event, no alcohol | 4-hour event with bar | 8-hour event with bar |
|---|---|---|---|
| 25 | 1 | 2 | 3 |
| 50 | 1 | 2 | 3 |
| 100 | 2 | 3 | 4 |
| 150 | 3 | 4 | 5 |
| 250 | 5 | 7 | 9 |
| 500 | 10 | 15 | 20 |
| 1,000 | 20 | 30 | 40 |
Worked example: 250 guests, 8 hours, bar. 250 ÷ 50 = 5 units. Four hours beyond the first 4 adds 1 unit per 100 guests, rounded down: +2. Alcohol adds 1 per 100, rounded down: +2. Total 9, of which 1 accessible (5% of 9 = 0.45, rounds up to 1). Add 2 handwash stations (1 per 4 units, with the food line in mind).
How many porta potties does a construction site need?
OSHA 29 CFR 1926.51(c) Table D-1 sets the legal minimum: 1 toilet for 20 or fewer workers, 1 seat and 1 urinal per 40 workers from 20 to 200, 1 seat and 1 urinal per 50 workers above 200. For usability, plan 1 standard unit per 10 workers on a 40-hour week, because a 60-gallon tank holds about 200 uses and is pumped weekly.
| Crew size | OSHA minimum | Recommended (weekly service) | Handwash stations |
|---|---|---|---|
| 5 | 1 toilet | 1 unit | 1 |
| 10 | 1 toilet | 1 unit | 1 |
| 20 | 1 toilet | 2 units | 1 |
| 40 | 1 seat + 1 urinal | 4 units | 1–2 |
| 80 | 2 seats + 2 urinals | 8 units | 2 |
| 150 | 4 seats + 4 urinals | 15 units | 4 |
Source: OSHA 1926.51. Agricultural sites: OSHA 1928.110 requires 1 toilet and 1 handwashing facility per 20 workers within a quarter-mile walk. Full detail on the OSHA requirements page.
Which adjustments change the count?
Four adjustments move the number: alcohol (+1 per 100 guests, rounded down, minimum 1), event length (the same addition for each 4 hours past the first 4), a mostly-female guest list (+1 unit, because sit-down use takes about twice as long), and a food line (add 1 handwash station per 4 units). Hot weather does not change the count but does justify a mid-event service.
- Bar open: +1 unit per 100 guests, rounded down, minimum 1.
- Over 4 hours: the same addition per extra 4-hour block.
- Mostly women: +1 unit.
- Food served: +1 handwash station per 4 units.
- Public event: 5% accessible per cluster, minimum 1.
- Over 150 guests or 6 hours: add a mid-event service visit rather than more units.
- House bathroom also open (private party): you can subtract 1 unit for groups under 75.
Trailers: one two-station trailer counts as roughly 3 standard units for a 5-hour reception. See trailer sizing.
Sizing questions
How many porta potties for 100 guests?
Two for a 4-hour party without a bar, three with a bar, and four if the event runs 8 hours with a bar. Make one of them accessible if the event is open to the public or an older guest needs it.
How many porta potties for a wedding of 150?
Five standard-class units for a 5-hour reception with a bar (3 for headcount, 1 for the extra hour, 1 for alcohol), one of them accessible. In practice most Butler weddings of 150 use one two-station trailer plus one flushable unit, which serves the same crowd with shorter lines.
How many for 75 people at a backyard graduation party?
Two units for a 4-hour party without a bar, three with one. If the house bathroom is open and the group is mostly family, one deluxe unit with a sink is usually enough.
How many for a 5K with 400 runners?
Eight standard units plus 1 accessible unit at the start/finish, because everyone needs the restroom in the same 30 minutes before the gun. Add 2 handwash stations if there is food at the finish.
How many for 130 employees during a 2-day water shut-off?
Three standard units and one handwash station, plus one accessible unit if any employee uses a chair. A standard unit covers about 50 users per day; three units cover 130 employees across two days without a mid-day service.
Does a restroom trailer replace several porta potties?
A two-station trailer serves about 150 guests over a 5-hour reception, roughly the work of 3 standard units, with running water and climate control. For crowds above 150, pair it with flushable units near the bar.
Price the units the calculator recommends
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