Free portable restroom calculator: how many porta potties?

The rules this calculator uses

These are common rental-industry rules of thumb, written down as the rules this page uses. They are not a standard, and rental companies chart them differently. Each one is a box in the rules section under the form, so change it to match what your rental company tells you.

• Base: one unit for every 50 guests at an event of up to 4 hours.
• Longer events: 12.5% more for each hour past 4, counted up to 12 hours. Past that, ask for service visits rather than more units.
• Alcohol: 1.5 times the units.
• Food: 1.1 times the units.
• Everyone arrives at once: 1.2 times the units, because the lines peak together.
• Women's share: 5% more for every 10 points above half the crowd, and 5% fewer for every 10 below.
• The venue's restrooms: each stall counts as one unit and each urinal as 0.5, only if guests can use them for the whole event.
• Accessible units: at least one, then one for every 20 units, counted inside the total.
• Hand-wash stations: one for every 4 units, at least one.
• A hot day: 10% more units, and never fewer than one extra.

The result is rounded up, since you cannot rent part of a unit. That is why 100 guests over 4 hours with a meal and no alcohol needs 3 units when the arithmetic says 2.2.

How many porta potties for 50 to 500 guests

This is an example, not a quote. It runs the calculator's own rules for five crowd sizes at 4 and 8 hours, with and without alcohol.

Read across for the effect of alcohol and down for the effect of the crowd. At 250 guests, 4 hours with alcohol needs 8 units against 5 without. At 500 guests over 8 hours with alcohol, it is 23. A meal adds 10% to any of these, and a crowd that arrives all at once adds 20%.

Why events with alcohol need more

Drinkers visit more often. Alcohol is a diuretic, and a bar means guests are taking in more liquid than they would at a dry event. The rule we use is 1.5 times the units, and it applies to the whole crowd because you rarely know in advance who will drink.

The lines also bunch up. They form after a toast, between a band's sets and when the bar closes. A crowd that was spread across the evening heads for the same doors at once, which is what the arrival box is for. If most of your guests will not drink, set the alcohol box lower, between 1 and 1.5, and see what the number does.

Where to put portable restrooms

The count only works if guests can find the units and use them without a long walk or a long line. A short checklist for the site walk:

• Near the entrance or the parking, so guests find them without asking.
• Within an easy walk of the bar and the seating, but not beside either. A line should not run through the bar queue.
• Away from food. Keep them well clear of where food is served or prepared, and ask the caterer and your local rules how far that is.
• On a lit path. If the event runs past dusk, plan lights along the route and ask the rental company about lighting inside the units.
• On level, firm ground with a clear way in for the delivery truck, and the same way out for the service truck.
• In more than one spot when you rent six or more units. Groups of a few keep one door from collecting every line.
• With the accessible unit at the front of its group, on a step-free route.
• With a hand-wash station beside each group, in view.

Accessible units and the path to them

An accessible unit is a larger portable restroom made for a wheelchair or another mobility aid. They are often called ADA units. The rule we use is at least one, then one for every 20 units, counted inside your total. Whether your event has to provide one, and how many, is for your city or county and your rental company to say. Ask early.

The unit helps nobody if guests cannot get to it. Plan a firm, level, step-free route from the entrance and the parking: no loose gravel, no soft grass, no curb. Where the ground is soft or slopes, ask the rental company what they can lay down. Put the unit at the front of its group with room to turn around outside it, and keep fences, cables and catering trucks away from the door.

Hand-washing and supplies

The rule we use is one hand-wash station for every 4 units, and at least one. Put it beside the units where guests will see it. Ask the rental company what the station holds, which is usually fresh water, waste water, soap and towels, and who refills it. Washing with soap and water is the better choice; sanitizer is a convenience for the line.

Ask who stocks the units and keep spares on site: toilet paper, paper towels, soap, trash bags and a bin outside the units.

What to ask the rental company

Give them your guests, hours, whether alcohol and food are served and the date. Many have their own chart. Compare it with this page's, and ask why if the two are far apart. Then ask:

• The delivery window. When the truck arrives, when it leaves, and when it comes back to pick the units up. Ask for a window that ends well before guests arrive.
• Service during the event. Whether a visit is included, what each one costs, and whether the truck can reach the units while guests are on site.
• A key or lock. Whether the units lock, who holds the key, and whether you want them shut until the event starts or overnight.
• An attendant. Whether one is available for a large or long event, what they do and what they charge by the hour.
• Power for lights. Whether the units have lights of their own or need power, and what the rental company wants from you for an evening event.
• Accessible units and hand-wash stations. How many they have for your date, and when to book.

Weather and ground

Grass. Units go on level, firm ground. After rain a lawn can soften enough to leave ruts under the truck or tilt a unit, so ask the venue about its ground rules and put the units on the firmest ground that is still near the crowd. Slopes. A unit on a slope is hard to use, and a slope also changes where the truck can go. Choose the flattest spot even if it is a few steps further.

Wind. An empty unit is light. Ask the rental company how it secures units on an open site, and tell them if the site is exposed. Hot days. Units heat up in full sun. Shade them if you can, and add units: the rule we use is 10% more, and never fewer than one extra. Cold. Ask whether the units and the hand-wash station are set up for freezing temperatures.

Permits and local rules

Rules differ by city and county. Some places require a permit for an event or for temporary sanitation, some set their own ratios, and some say how far units must sit from food, water or a property line. Ask the venue first, since the venue knows its own capacity and limits. Then ask the city or county. Your rental company often knows the local requirements and may be able to tell you what they have delivered for similar events.

This page gives a planning count. It is not a permit application and not legal advice, so do not rely on it where a local authority sets the number.

For venues and planners

An outdoor or tent event adds a restroom line to the budget and to the site plan. The budget line is the rental, delivery, service visits, an attendant and the hand-wash station. The site plan line is where the units go and how the truck gets there.

Mark the units on the floor plan, so the rental company, the caterer and the bar all see the same spot. Size the rest of the site with the free tent size calculator, check the guest count against the room with the free venue capacity calculator, and draw the layout in the free event floor plan maker. If guests will use your own restrooms, count the stalls and urinals and put them in the calculator, so the rental covers only what is left.

MyVenueHQ keeps the layout, the vendor list and the BEO on one event, so the restroom rental sits next to the tent and the caterer.

Add this portable restroom calculator to your website

Venues, planners and wedding blogs can put it on their own site for free. Paste this where you want it; it works in WordPress, Squarespace, Wix and plain HTML. Nothing is tracked about your visitors beyond page views.