Short answer: Take your event’s length in hours and your peak guest count, and read the number off the calculator below — it’s the chart we’ve quoted from across years of real Central Texas events. Add 15–20% if alcohol is served, another 15–20% for food service, one ADA-certified unit per four restrooms, and one handwash station per four restrooms. For permitted public events, the City of Austin works to one unit per 50 people at peak attendance — where that’s more than the calculator, the permit number wins.
A 150-guest wedding running six hours with an open bar and dinner: four standard units, or a single restroom trailer.
Below is the calculator, the adjustments that move the number, and the two things most guidance on this topic gets wrong.
The event rental calculator
Search this question and you’ll find flat rules of thumb — one unit per 50 guests, one per 100. They ignore the variable that matters most: how long your event runs. A two-hour ceremony and a ten-hour festival with the same guest count are completely different restroom problems.
This is the calculator we quote from. Find your event’s length in hours across the top and your guest count down the side. If your event runs multiple days, use the longest day; for guest count, use the day with the largest attendance, at its peak.
| Guests ↓ / Hours → | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| 50 | 1 | 1 | 1 | 1 | 2 | 2 | 2 | 2 | 2 | 2 |
| 100 | 2 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 |
| 250 | 2 | 2 | 2 | 2 | 3 | 3 | 3 | 3 | 3 | 3 |
| 500 | 2 | 4 | 4 | 5 | 6 | 7 | 9 | 9 | 10 | 12 |
| 1,000 | 4 | 6 | 8 | 8 | 9 | 9 | 11 | 12 | 13 | 13 |
| 2,000 | 5 | 6 | 9 | 12 | 14 | 16 | 18 | 20 | 23 | 25 |
| 3,000 | 6 | 9 | 12 | 16 | 20 | 24 | 26 | 30 | 34 | 38 |
| 4,000 | 8 | 13 | 16 | 22 | 25 | 30 | 35 | 40 | 45 | 50 |
| 5,000 | 12 | 15 | 20 | 25 | 31 | 38 | 44 | 50 | 56 | 63 |
| 6,000 | 12 | 15 | 23 | 30 | 38 | 45 | 53 | 60 | 68 | 75 |
| 7,000 | 12 | 18 | 26 | 35 | 44 | 53 | 61 | 70 | 79 | 88 |
| 8,000 | 12 | 20 | 30 | 40 | 50 | 60 | 70 | 80 | 90 | 100 |
| 10,000 | 15 | 25 | 38 | 50 | 63 | 75 | 88 | 100 | 113 | 125 |
Guest counts between rows: use the nearer row, rounding up if you’re close to halfway. These are working numbers from real events, not theoretical ratios — and every adjustment below moves them up, never down.
The three adjustments that matter
Alcohol. Add 15–20% more restrooms if alcohol is being served. A cash bar sits at the low end; a sustained open bar at the high end.
Food and drink service. Add another 15–20% where there’s food service. Meals increase both usage and the hygiene expectation — and food service is what triggers handwashing requirements, covered below.
Crowd composition. Women’s restroom visits take longer, so events skewing heavily female — bridal showers, quinceañeras, many weddings — run short at the same unit count. If your guest list is 70% women, read the calculator as though you had 20% more guests.
Worked example. 150 guests, six-hour wedding, open bar, dinner served. Calculator at six hours: 3 units (between the 100 and 250 rows). Open bar: +20% → 3.6. Food service: nudge again. Four standard units — or one restroom trailer (a 2-stall Pro covers up to 225 guests, a 3-stall Eco up to 250).
OSHA does not apply to your guests
This is the most common error in guidance on this topic, and it appears on portable sanitation company websites across Texas.
OSHA’s sanitation standard, 29 CFR 1926.51, governs employees at construction jobsites. It does not set requirements for members of the public attending an event. An event with 500 guests and a dozen staff has no OSHA-mandated guest restroom count.
Where OSHA can apply to an event is your crew — vendors, caterers, production staff, build and strike teams working the site. If you have workers on site for a multi-day build, employer sanitation obligations attach to those workers. We’ve covered what OSHA actually requires on a job site separately.
For guests, the framework is different: PSAI industry guidance, the venue’s own requirements, and — this is the part that has actual force — local permit conditions.
The City of Austin’s rule is more specific than most people realize
The City of Austin’s special event guidance recommends one chemical or portable toilet per 50 people, and it specifies that the count should be based on estimated peak attendance, not total attendance across the day.
That distinction matters and almost nobody applies it. A festival with 2,000 people passing through over eight hours but never more than 600 on site at once is a 600-person restroom problem, not a 2,000-person one. Conversely, a wedding where all 150 guests are present the entire time has peak attendance equal to total attendance.
Two further points from the same guidance:
- You must provide portable restroom facilities unless you can substantiate that sufficient accessible and non-accessible facilities already exist in the immediate area and will be available to the public during your event.
- If only one restroom is placed in a location, it must be accessible. This catches people out on small events and satellite placements — a single unit at a remote corner of a site has to be the ADA model.
One important bridge between the calculator and the permit: where the City’s one-per-50-at-peak works out higher than the calculator, the permit number wins. A permitted 250-person public event needs five units under the City’s guidance even where the calculator reads three — the calculator is our working chart for private events; the permit condition is a legal requirement.
Requirements vary by jurisdiction. Events in Round Rock, Georgetown, Cedar Park or unincorporated Williamson, Travis, Hays and Bell Counties work to different processes, and county-level events may involve the Fire Marshal’s office. If your event is permitted, confirm the restroom condition in writing before you book — permit officers can and do require more units than you planned for.
ADA-certified units
Our working recommendation for events is one ADA unit per four standard units, and at least one at any event open to the public regardless of size. It’s a more generous provision than the industry’s one-per-twenty note, and it’s the ratio we build into event quotes.
One wording point worth knowing: the units we stock are ADA certified, not merely “ADA accessible” — certification means the unit itself meets the standard, rather than being loosely described as accessible.
An ADA portable restroom is considerably larger than a standard unit — ours measure 66 inches wide by 86.5 inches deep, with a 32.7-inch doorway, against 44 by 48 inches and a 24-inch door on a standard unit. Ground-level entry, a larger interior turning radius and handrails come as standard. It counts toward your total unit number; it isn’t an addition on top.
For events where accessibility matters and a plastic unit isn’t the right look, we also run an ADA-certified restroom trailer — three stations including a fully accessible one, supporting up to 200 guests over a six-hour event. It’s the option most event planners don’t know exists.
Two placement points that get missed: the accessible unit needs a firm, level approach, not turf or gravel, and it should be positioned on the same accessible route as the rest of the event, not tucked behind the ones everybody else uses.
Handwashing stations
Our standard is a minimum of one handwash station per four restrooms — the same ratio as the ADA provision, which makes the arithmetic easy: for every four restrooms, add one ADA unit and one sink.
Food service raises this from good practice to a requirement. In Austin and Travis County, a Temporary Food Event Permit is required whenever food or drinks are offered to the public at an event, and handwashing provision is part of what’s inspected. If you’re running food trucks, a caterer serving from a tent, or any public food service, factor handwashing capacity in from the start rather than adding it after the permit review.
Our handwash stations are two-sink units with soap and paper towels, delivered filled and ready to use — no water hookup needed on site. Restroom trailers include sinks with running water, which changes the calculation again: a trailer with three sinks is already meeting part of the handwashing requirement.
Standard units or a restroom trailer?
The count is only half the decision. Guest expectation is the other half, and for weddings and upscale events a trailer is usually the answer.
We run thirteen restroom trailer configurations. Guest capacities below are for a six-hour event:
| Trailer | Stations | Guest capacity | Waste tank |
|---|---|---|---|
| 2-stall Eco | 2 | Up to 150 | 200 gal |
| 2-stall Pro | 2 | Up to 225 | 300 gal |
| 3-stall Eco | 3 | Up to 250 | 350 gal |
| 3-stall Pro | 3 | Up to 325 | 400 gal |
| ADA 1+2 | 3 (1 accessible) | Up to 200 | 345 gal |
| 4-station private | 4 | Up to 250 | 350 gal |
| 4-station community | 4 | Up to 250 | 350 gal |
| 5-station Pro | 5 | Up to 350 | 520 gal |
| 6-station community | 6 | 250–500 | 680 gal |
| 7-station | 7 | 500–750 | 680 gal |
| 8-station | 8 | 750–1,000 | 715 gal |
Eco and Pro are the same stall count in different sizes. A Pro trailer is longer, carries a bigger waste tank and supports meaningfully more guests — a 3-stall Pro handles 325 where the Eco handles 250. If your numbers sit awkwardly between two trailer sizes, the Pro version of the smaller one is often the answer.
Trailers have flushing toilets, running water, climate control and interior lighting. For a summer wedding in Central Texas, climate control is not a luxury item — an un-airconditioned unit in August is a genuinely unpleasant experience and guests will avoid it, which concentrates usage elsewhere.
Between a basic unit and a full trailer sits the deluxe portable restroom, which is often the right answer for mid-range events. We’ve covered what makes a deluxe event porta potty different separately.
Mixing unit types works well. A common setup for a 250-guest wedding: one 3-stall trailer near the reception area, plus two standard units at the parking and ceremony end, plus one ADA unit. Guests get the trailer experience where it matters and coverage where it doesn’t.
Private or community: what the entrance count tells you
Restroom trailers are described by the number of stalls or stations they contain, but that number alone doesn’t tell you how the space is arranged. The arrangement is what your guests actually experience, and it’s rarely explained.
Private configuration means each exterior door opens into a complete, self-contained bathroom. One person, one room, one lock. Our 4-station private trailer has four separate exterior entrances — four fully private bathrooms, used one at a time.
Community configuration works the way a conventional public restroom does: gender-marked entrances — one entry per gender regardless of the station count — each leading to a shared interior with multiple stalls. Our 4-station community trailer has two exterior entrances, one per gender.
Both hold four stations and both support up to 250 guests. They feel completely different to use.
Which to choose:
- Private suits weddings and upscale events, where guests are dressed formally and privacy is part of the experience. Every room is single-occupancy, so there’s no gendered entrance at all.
- Community suits higher-throughput events — festivals, races, corporate functions — where turnover matters more than privacy. A shared interior with multiple stalls moves more people per hour than the same number of individual rooms.
Above four stations, the larger trailers are all community configuration, which is what allows them to serve up to a thousand guests.
If you’re weighing the two, tell us the event type and we’ll tell you which we’d send.
Power and water
Standard portable restrooms need neither. They’re self-contained, delivered filled and ready, and can go anywhere a truck can reach.
Restroom trailers need electricity and water. Most of our trailers run on a single 20-amp connection — an ordinary household circuit, not a generator-grade supply. If your venue has no power or no water, which covers a lot of ranch properties, open fields and Hill Country wedding sites, we supply a generator and on-board freshwater tanks filled at delivery. Confirm this at the quote stage rather than on the day; it changes the delivery setup.
Trailers also need towing access and reasonably level ground. Our trailers want a firm surface level within about three inches across the width, with no more than an 18-inch fall front to back, and roughly 10 feet of access width to get in. If you’re unsure whether a site works, send a photo.
For multi-day events, or single events with heavy usage, waste holding tanks and freshwater tanks extend capacity without adding units.
Multi-day events and overnight servicing
A trailer that’s comfortable on Friday evening is not automatically comfortable on Sunday afternoon. Waste tank capacity, not stall count, is usually the limiting factor across a multi-day event — which is why the tank figures are in the table above.
We service units overnight or early in the morning between event days, which is standard practice on festivals and multi-day builds. Pumping happens outside event hours so guests never see it and the units reset to full capacity each day.
If you’re planning a multi-day event, tell us the running order and daily attendance rather than just the headline total. A three-day festival with 800 people a day is a different servicing problem from a single-day event with 2,400.
Placement
- Spread units out. Clustering everything in one location creates a single queue and one congested area. Splitting across two or three points distributes traffic.
- Keep them away from food service and dining, both for hygiene and for the obvious reason.
- Level ground. Trailers in particular need a level, firm base, and towing access to reach it.
- Think about lighting. An unlit restroom area at an evening event effectively stops being available after dark. Trailers have interior lighting; standard units don’t.
- Signage. If guests can’t find them, they’ll queue at the ones they can.
When to book — and how fast we can deliver
Two different questions, often confused.
Delivery is fast, in any season. Porta potties deliver next-day as standard, or same-day with a fee. Trailers off-peak deliver same-day with a fee or next-day without — though a few days’ notice always helps us plan access.
Booking ahead is about choice, not speed. March, April, May, October and November are wedding and festival season across the Hill Country and Williamson, Travis, Hays and Bell Counties, and weekends in those months historically sell out. Restroom trailers go first, because there are fewer of them. For a peak-season Saturday, book six to eight weeks ahead to secure the trailer you actually want — not because delivery takes that long, but because by a month out it may already be committed to someone else.
Central Texas seasonality
From June through September, heat raises water consumption, accelerates odor, and makes climate-controlled units substantially more attractive to guests. For multi-day summer events, plan for more frequent servicing than you would in spring — and expect trailers to be in higher demand than the booking calendar alone suggests.
Quick reference
| Factor | Adjustment |
|---|---|
| Base count | Calculator above — hours × peak guest count |
| Alcohol served | +15–20% |
| Food and drink service | +15–20% |
| Heavily female crowd | Read calculator as +20% guests |
| ADA-certified units | 1 per 4 standard units; minimum 1 at public events |
| Handwashing | Minimum 1 station per 4 restrooms |
| City of Austin permit guidance | 1 per 50 at peak attendance — wins where higher |
| Single unit at a location | Must be the ADA-certified model |
| Delivery — any season | Porta potties next-day standard, same-day with fee |
| Peak trailer booking (Mar–May, Oct–Nov) | 6–8 weeks to secure your choice; weekends sell out |
Frequently asked questions
How many porta potties do I need for 100 guests?
From the calculator: two units for events up to five hours, three from six hours. Add one more where there’s a bar. For 100 guests at a wedding, a 2-stall restroom trailer covers it comfortably.
How many portable toilets for 250 guests?
From the calculator: two to three standard units depending on hours, plus 15–20% where alcohol is served. For a permitted public event in Austin, the City’s one-per-50-at-peak rule takes it to five. On the trailer side, a 3-stall Eco, a 4-station private or a 4-station community trailer each supports up to 250 guests over six hours.
How many porta potties for 500 guests?
From the calculator: five units at four hours, seven at six, twelve for a ten-hour day — plus 15–20% for alcohol and the same again for food service. A permitted Austin event works to ten under the City’s peak-attendance rule. A single 6-station community trailer covers 250 to 500 guests, and a 7-station covers 500 to 750. At this size, plan one ADA-certified unit and one handwash station per four restrooms.
What do you have for events over 750 guests?
Our 8-station restroom trailer supports 750 to 1,000 guests over a six-hour event, with a 715-gallon waste tank. On standard units, the calculator reads nine at 1,000 guests for six hours before adjustments. For larger crowds or multi-day festivals we combine trailers with standard units and schedule overnight servicing between days — and for crowds in the thousands, the calculator above runs to 10,000 guests.
Does OSHA set how many portable toilets an event needs?
No. OSHA’s sanitation standard covers employees at workplaces and construction jobsites, not guests at an event. Event restroom counts come from PSAI industry guidance and local permit conditions. OSHA obligations can apply to your event crew — vendors, caterers, build and strike teams.
How many portable toilets does the City of Austin require?
Austin’s special event guidance recommends one chemical or portable toilet per 50 people, based on estimated peak attendance. Facilities must be provided unless sufficient existing accessible and non-accessible restrooms are available nearby during the event. Where only one restroom is placed at a location, it must be accessible.
Do I need more porta potties if I’m serving alcohol?
Yes. Alcohol increases restroom usage — add 15–20% more restrooms when it’s served, toward the top of that range for a sustained open bar.
What’s the difference between a private and a community restroom trailer?
Private means each exterior door opens into a complete, self-contained bathroom used by one person at a time. Community works like a conventional public restroom: gender-marked entrances — one per gender regardless of station count — each leading to a shared interior with multiple stalls. Our 4-station private trailer has four exterior entrances; our 4-station community trailer has two, one per gender. Both support up to 250 guests, but private suits weddings and upscale events while community moves more people per hour.
What’s the difference between an Eco and a Pro restroom trailer?
Same stall count, different size. A Pro trailer is longer and carries a larger waste tank, so it supports more guests — our 3-stall Pro handles up to 325 guests against 250 for the 3-stall Eco, and the 2-stall Pro handles 225 against 150. If your guest count sits between two trailer sizes, the Pro version of the smaller trailer is often the better fit.
Do you have an ADA-certified restroom trailer?
Yes. Our ADA-certified 1+2 trailer has three stations including one fully accessible, and supports up to 200 guests over a six-hour event. It’s an alternative to placing a plastic ADA unit alongside a trailer, and it keeps every guest using the same facility.
How many handwashing stations do I need?
A minimum of one handwash station per four restrooms — the same ratio as the ADA provision, so for every four restrooms, add one ADA unit and one sink. Our stations are two-sink units with soap and paper towels, delivered filled and requiring no water hookup. If food or drink is served to the public in Austin or Travis County, a Temporary Food Event Permit applies and handwashing provision forms part of it.
Do restroom trailers need power and water?
Yes. Most of our trailers run on a single 20-amp connection, which an ordinary household circuit will supply, plus a water source. Where a venue has neither, we supply a generator and on-board freshwater tanks filled at delivery. Standard portable restrooms need neither power nor water.
Can you service restrooms overnight during a multi-day event?
Yes. We pump and service units late at night or early in the morning between event days, so the work happens outside event hours and units reset to full capacity each day. For multi-day events, tell us daily attendance rather than the headline total.
How far in advance should I book portable toilets for an event?
Delivery itself is fast: porta potties next-day as standard or same-day with a fee, in any season; trailers off-peak same-day with a fee or next-day without. Booking ahead is about securing your choice — for March, April, May, October and November, book six to eight weeks out, because weekends in those months historically sell out and restroom trailers go first.
Work out your count with us
Tell us guest numbers, how long the event runs, whether there’s a bar, and where the site is — we’ll tell you what you need and what it costs. We supply event restroom rentals across Austin, the Hill Country and Williamson County, from single units at a backyard party to trailer setups at 1,000-guest events.
Call or text 512-643-7286, or request a quote.