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How Many Porta Potties Do You Need?
Start with 1 porta potty for every 50 guests at an event of up to 4 hours. Add half that count again for each extra 4 hours. Add one more unit for every 4 when you serve alcohol. Crews follow a different rule, so switch the calculator below to job site mode for those numbers.
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Porta potty calculator for events and crews
The porta potty calculator below needs 3 inputs: what you are planning, the head count and the hours. Tick the boxes for alcohol, food or guests who use wheelchairs. The answer updates as you type. Each step shows, so you can check the math yourself before you book.
What the calculator assumes
- Events use the Willie Rental Works method. One unit covers 50 guests for 4 hours. Each extra block of up to 4 hours adds half the base, at least 1.
- Alcohol raises the count. A bar or keg adds 1 unit per 4 toilets, with a minimum of 1.
- Food adds sinks. Plan 1 hand wash station per 3 toilets when people eat with their hands.
- Accessible units count inside the total. The 2010 ADA Standards, section 213.2, ask for 5% of each cluster, minimum 1.
- Crews use OSHA as the floor. OSHA 1926.51 Table D-1 sets the legal minimum. We then apply 1 unit per 10 workers for a 40-hour week with weekly service.
How many porta potties per person?
Plan 1 porta potty per 50 people for an event of 4 hours or less. That works out to 2 units for 100 guests and 4 units for 200. Longer events, a bar and hot weather all push the count up. A job site works per worker instead, at about 1 unit per 10.
| Guests | Up to 4 h | 5–8 h | 9–12 h |
|---|---|---|---|
| 25 | 1 | 2 | 3 |
| 50 | 1 | 2 | 3 |
| 75 | 2 | 3 | 4 |
| 100 | 2 | 3 | 4 |
| 150 | 3 | 5 | 7 |
| 200 | 4 | 6 | 8 |
| 250 | 5 | 8 | 11 |
| 300 | 6 | 9 | 12 |
| Guests | Up to 4 h | 5–8 h | 9–12 h |
|---|---|---|---|
| 25 | 2 | 3 | 4 |
| 50 | 2 | 3 | 4 |
| 75 | 3 | 4 | 5 |
| 100 | 3 | 4 | 5 |
| 150 | 4 | 7 | 9 |
| 200 | 5 | 8 | 10 |
| 250 | 7 | 10 | 14 |
| 300 | 8 | 12 | 15 |
Read the tables by row, then column. A 200-guest picnic from noon to 6 PM lands in the 5–8 hour column. That picnic needs 6 units. Pour beer at that picnic and the count becomes 8.
Worked example, backyard birthday: 60 people come for 5 hours. The base is 60 ÷ 50, rounded up to 2. Five hours adds half of 2, so the method says 3.
A house bathroom open to guests can absorb some of that use. Count the house as 1 of the 3, and rent 2 outdoor units. For a mostly adult crowd, a standard event porta potty handles the job.
How many porta potties for a wedding?
A 150-guest wedding of 5 hours with a bar needs 7 toilets by the Willie Rental Works method. The base is 3, the fifth hour adds 2, and the bar adds 2 more. A 2-stall restroom trailer counts as 2 of those 7 toilets. The trailer plus 5 units covers the night.
Here is that math step by step. 150 ÷ 50 = 3 units for the first 4 hours. The fifth hour starts a new block, so add half of 3, rounded up to 2.
That makes 5. Alcohol adds 5 × 0.25, rounded up to 2, for 7 total. Dinner means 7 ÷ 3, rounded up, so plan 3 hand wash stations.
Mixing a trailer with single units
Many couples put the trailer near the dance floor and units by the parking area. Elderly guests and the wedding party use the trailer. See the wedding restroom options or the 2-stall restroom trailer power and water needs.
How many porta potties for a job site?
OSHA Table D-1 sets a floor of 1 toilet for a crew of 20 or fewer. We plan 1 unit per 10 workers on a 40-hour week with weekly service. A 14-person framing crew therefore gets 2 units. Crews past 40 hours a week need a third unit or a second service.
OSHA sets the legal floor, but that floor assumes nothing about how fast a tank fills. Fourteen workers on a 50-hour week will overflow 1 unit before the service day.
The calculator's job site mode adds 50% more units when crew hours pass 40 a week. Our plain-English OSHA porta potty requirements page walks through every row of the table. Ready to order? See construction porta potty rental.
How many hand wash stations do I need?
Plan 1 hand wash station for every 3 toilets when food is served. Six toilets at a fish fry means 2 stations. Without food, the calculator suggests 1 station per 5 toilets once you reach 4 units. A single PolyJohn Bravo station gives nearly 350 uses per fill, says the manufacturer.
Units with a sink inside also count toward hand washing. They make sense for small parties where one sink per toilet is enough.
Set stations between the toilets and the food line, not behind the units. See the hand washing station rental page for specs.
When should one unit be accessible?
Make at least 1 unit wheelchair-accessible when a guest uses a wheelchair. Do the same for any public event. The 2010 ADA Standards ask for 5% of each cluster, minimum 1. A cluster of 20 or fewer toilets needs 1 accessible unit. A cluster of 21 to 40 needs 2.
The accessible unit counts inside your total. It is not an extra on top. Walkers, strollers and parents helping small children use it too.
The unit is 62 inches square, so it needs a wider flat spot than a standard one. Read about the wheelchair-accessible porta potty before you pick the spot.
Porta potty count questions
These 6 answers cover head-count questions that the tables above leave open. Topics include house bathrooms, trailers, kids, overnight events and cost. Each answer starts with a number or a rule. For prices on every unit type, read the porta potty rental cost guide.
I have 75 people and one bathroom in the house. Do I need two?
The method gives 2 units for 75 guests over 4 hours or less. If guests can use the house bathroom, it can stand in for 1 of them. Rent 1 outdoor unit for a short party. Rent 2 if the party runs past 4 hours or has a bar.
Does a restroom trailer count as two units?
A 2-stall restroom trailer counts as 2 toilets in the count, one per stall. A 150-guest wedding needing 7 toilets could use 1 trailer and 5 single units. Trailer rental starts at $1,195 for the weekend. That price covers delivery, setup and pickup inside 25 miles of Conroe.
Do kids count the same as adults?
Count every child as a full guest. Kids use the restroom often and take longer inside. For a party with lots of small children, a unit with a sink inside helps parents with handwashing.
What if I guess low on the count?
A low count means lines and a full tank before the party ends. Rounding up by 1 unit costs less than a mid-event service visit at $45. Same-day add-ons are possible when you call by 12 PM, Monday through Saturday.
We're camping out for 2 nights. How do I count that?
Treat each 24-hour day as its own event and run the calculator with the full hours. Multi-day events get a service visit between days, which resets the tanks. Tell us the schedule, and we time service before the busiest day.
How much will 4 event units cost?
Standard event units start at $195 each per weekend, plus $60 for delivery and pickup. Four units start at $780 plus delivery and Texas sales tax. Outer areas add a distance charge.
Get a quote for your head count
A quote for your head count needs 4 things: the guest or crew number, the hours, the ZIP code and the date. Send the calculator result with the form, and we check it against your site. The quote lists units, sinks, delivery and tax as separate lines.
Calls answered live Mon–Sat, 7 AM–7 PM. Online quotes answered within 30 minutes.
Have your count?
Call with the number and the date, and we will price every unit on the phone.
Calls answered live Mon–Sat, 7 AM–7 PM. Online quotes answered within 30 minutes.