How Many Porta Potties Do I Need?
You need 1 porta potty per 50 guests for an event up to 4 hours, 1 per 40 guests for 5–8 hours, and 1 per 30 for longer days. Add 1 unit for every 5 when alcohol is served. Use the calculator below for your exact count.
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- Delivery area
- We deliver the count you need anywhere in Milwaukee County and nearby suburbs.
- Arrival
- Up to 4 units same-day when you call by noon; larger orders, call 1–2 weeks ahead.
- Which unit
- Count standard-unit equivalents first, then swap in deluxe, accessible or trailers.
- Cleaning
- Multi-day events need a service visit each day of heavy use.
- Full cost
- Price = unit count × unit rate. See the pricing guide.
Porta potty calculator
Enter your guest count and event length, then tick alcohol, food and public access. The porta potty calculator applies our sizing method step by step — base units, the alcohol add-on, accessible units under ADA §213.2, and handwashing stations — and shows the math.
- 150 guests ÷ 40 guests per unit (5–8 hours) = 4 units (rounded up)
- Alcohol served: add 1 unit for every 5 → +1
- Make 1 of them wheelchair-accessible (at least 1 in every 20, ADA §213.2 for events open to the public)
- Handwashing: 2 stations (1 per 4 toilets)
How many porta potties per person?
Plan 1 porta potty per 50 people for events up to 4 hours, 1 per 40 people for events of 5 to 8 hours, and 1 per 30 people for events of 9 hours or more. Round up every time. These ratios are the Walter Rental Works sizing method, based on a standard unit's roughly 200-use tank.
| Guests | Up to 4 h | 5–8 h | 9+ h | 5–8 h + alcohol |
|---|---|---|---|---|
| 25 | 1 | 1 | 1 | 2 |
| 50 | 1 | 2 | 2 | 3 |
| 75 | 2 | 2 | 3 | 3 |
| 100 | 2 | 3 | 4 | 4 |
| 150 | 3 | 4 | 5 | 5 |
| 200 | 4 | 5 | 7 | 6 |
| 250 | 5 | 7 | 9 | 8 |
| 300 | 6 | 8 | 10 | 9 |
| 400 | 8 | 10 | 14 | 12 |
| 500 | 10 | 13 | 17 | 15 |
| 750 | 15 | 19 | 25 | 22 |
| 1000 | 20 | 25 | 34 | 30 |
Why these numbers?
A standard unit holds about 200 uses before it needs pumping. The average guest uses a restroom about once every 2 hours, and more often when drinking. Our ratios keep each unit under its tank limit with room to spare, so lines stay short and units stay clean to the end.
Worked example: 150-guest wedding with a bar
A 150-guest, 5-hour wedding with a bar needs 5 standard porta potties. The base count is 150 ÷ 40 = 3.75, rounded up to 4. Alcohol adds 1 unit for every 5 base units, minimum 1, so 4 + 1 = 5. Make 1 of the 5 accessible if guests may use wheelchairs, and add 2 handwashing stations.
- Base count 150 guests ÷ 40 (5-hour event) = 3.75 → round up to 4 units.
- Alcohol add-on 4 base units ÷ 5 = 0.8 → minimum 1 → add 1 unit. Total 5.
- Accessible units 5 units is a cluster of under 20 → at least 1 accessible (ADA §213.2).
- Handwashing 5 ÷ 4 = 1.25 → round up to 2 stations; add 1 more by the food if catered.
- Upgrade option Swap all 5 for one 2-stall restroom trailer + 1 accessible unit.
Do construction crews use the same chart?
No. Construction crews are sized by worker count under OSHA 29 CFR 1926.51(c), not by guest ratios: 1 toilet for 20 or fewer workers, then 1 seat and 1 urinal per 40 workers. Farm field crews use OSHA 1928.110 instead. The full rules are in our Wisconsin jobsite toilet guide.
| Workers | Construction (1926.51) | Farm field crew (1928.110) |
|---|---|---|
| 1–20 | 1 toilet | 1 toilet + 1 handwashing |
| 21–40 | 1 seat + 1 urinal | 2 toilets + 2 handwashing |
| 41–80 | 2 seats + 2 urinals | 3–4 toilets + 3–4 handwashing |
| 200 | 4 seats + 4 urinals | 10 toilets + 10 handwashing |
Official texts: 29 CFR 1926.51 · 29 CFR 1928.110. Full guide: Wisconsin jobsite toilet requirements.
When should I add more units?
Add 1 more porta potty than the chart shows when most guests are women or children, when the event is a hot July or August day, when the units sit far apart, or when there is no indoor bathroom at all. These four conditions shorten the time between uses, so the chart's count runs tight.
From the U.S. call study: Callers often asked "Is one enough?" — like the host told by an Airbnb owner that two were required for 40 guests, or the church with 55 people and one indoor restroom. Our rule of thumb from those calls: if there is no indoor bathroom, use the chart as-is; if there is one, you can subtract 1 unit for groups under 100.
Questions about this guide
There will be 120 people. How many do I need?
For 120 people over 4 hours, 3 units (120 ÷ 50 = 2.4, round up). Over 5–8 hours, 3 units (120 ÷ 40 = 3). Add 1 if there is a bar.
How many people does one porta potty accommodate?
One standard porta potty serves about 50 people for 4 hours, 40 people for 8 hours, or about 200 uses before it needs pumping.
What would you recommend for a large event of about a thousand people?
For 1,000 people over 5–8 hours with alcohol, 30 standard units by our method (1,000 ÷ 40 = 25, plus 5 for alcohol), of which at least 2 should be accessible, plus 8 handwashing stations, with a mid-event service on all-day events. Call us; we plan the layout too.
We have a facility with one restroom and 55 people. Is one extra unit enough?
Yes for a 4-hour event. 55 people with one indoor restroom plus one porta potty keeps lines short.
How many porta potties for 460 people at a shelter or multi-day site?
For round-the-clock use, plan about 1 unit per 30 people — 16 units — with daily service, plus handwashing stations. Restroom trailers can replace part of the row.
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