Free porta potty calculator
How Many Porta Potties Do I Need?
Enter your guest count or crew size and get a whole-number answer, including wheelchair-accessible units and handwashing stations. The method and its sources are written out below.
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Porta potty calculator
Most events need 1 porta potty per 50 guests for up to 4 hours. Add 50% more units, rounded up, when the event runs longer than 4 hours, and add 1 unit when alcohol is served (2 above 200 guests). Construction crews follow the Michigan rule instead.
How is the porta potty count calculated?
The porta potty count starts at 1 unit per 50 guests for up to 4 hours, our standard sizing method for Metro Detroit events. For events longer than 4 hours, add 50 percent more units, rounded up. If alcohol is served, add 1 unit, or 2 units above 200 guests. Then add accessible units and handwashing stations.
| Guests | Up to 4 hrs | 5–8 hrs | 5–8 hrs + alcohol | Accessible units | Handwashing (food served) |
|---|---|---|---|---|---|
| 25 | 1 | 2 | 3 | 1 | 1 |
| 50 | 1 | 2 | 3 | 1 | 1 |
| 75 | 2 | 3 | 4 | 1 | 1 |
| 100 | 2 | 3 | 4 | 1 | 1 |
| 150 | 3 | 5 | 6 | 1 | 2 |
| 200 | 4 | 6 | 7 | 1 | 2 |
| 250 | 5 | 8 | 10 | 1 | 3 |
| 300 | 6 | 9 | 11 | 1 | 3 |
| 400 | 8 | 12 | 14 | 1 | 4 |
| 500 | 10 | 15 | 17 | 1 | 5 |
Worked example
A 150-guest wedding lasting 6 hours with a bar: 150 ÷ 50 = 3 units. The event runs past 4 hours, so add half of 3, rounded up, which is 2: now 5 units. Alcohol is served, so add 1: 6 units. Five percent of 6, rounded up, is 1 wheelchair-accessible unit. Food is served, so 6 ÷ 4, rounded up, is 2 handwashing stations.
What are the legal minimums in Detroit and Michigan?
Detroit permitted special events must provide at least 1 portable restroom per 100 attendees and 1 handwashing station per 4–5 restrooms. Michigan construction sites need 1 toilet for up to 20 workers, 2 for 21–40, and 1 more per additional 40. Public events need at least 5 percent of each cluster to be wheelchair accessible.
| Situation | Legal minimum | Official source |
|---|---|---|
| Detroit special event | 1 restroom per 100 attendees; 1 handwashing station per 4–5 restrooms | City of Detroit Special Events Applicant Guide |
| Michigan construction site | 1 toilet (1–20 workers), 2 (21–40), +1 per 40 more | Mich. Admin. Code R 408.40129 |
| Federal construction (comparison) | 1 toilet (≤20); 1 toilet + 1 urinal per 40 (20–199); per 50 (200+) | OSHA 29 CFR 1926.51(c) |
| Accessible units at public events | At least 5% of each cluster, minimum 1 | 2010 ADA Standards §213.2 |
Legal minimums are a floor, not a comfort level. Our recommendation from the calculator is usually higher. Confirm your event’s rules with the city, venue or permit office; this page is not legal advice.
Next steps: compare standard units, wheelchair-accessible units and handwashing stations, then check the full Detroit price guide or the Detroit permit rules.
How many porta potties do I need? More answers
How many porta potties do I need for 200 guests?
Four porta potties cover 200 guests for up to 4 hours. For a 6-hour event, add 2 more units for 6, and add 1 more if alcohol is served for 7. Include at least 1 wheelchair-accessible unit and 1–2 handwashing stations when food is served.
How many porta potties do I need for 50 people?
One porta potty covers 50 people for up to 4 hours. Rent 2 if the event runs longer than 4 hours or if alcohol is served.
Do I need separate porta potties for men and women?
Not required for private events. At events over about 150 guests, marking one or two units for women and adding a urinal-heavy standard unit for men shortens lines.
How many porta potties for a 10-person construction crew?
One porta potty covers a crew of up to 20 workers under Michigan rule R 408.40129. With 10 workers on long shifts, one unit with weekly service is enough; add a mid-week service if the crew works 6 days.
How many handwashing stations do I need?
Plan 1 handwashing station per 4 to 5 portable toilets, and add 1 at each food line. The City of Detroit special-events guide uses the same ratio.
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