Start with three questions
- How many people will be there at the same time?
- How long will the event or shift last?
- Will people be drinking, eating, or both?
A rough planning heuristic for events
The figures below are a common planning heuristic, not a legal standard or a guarantee. They assume a mixed crowd, and every event is different. Treat them as the lower end of what to ask about, and adjust upward for the factors in the next section.
| Guests | Event of about 4 hours | Event of about 8 hours |
|---|---|---|
| 50 | 1–2 units | 2 units |
| 100 | 2 units | 3–4 units |
| 250 | 4–5 units | 6–8 units |
| 500 | 8–10 units | 12–15 units |
| 1,000 | 14–20 units | 22–30 units |
What pushes the number up
- Alcohol service, which increases visits per guest
- Events with a long meal or a break when everyone goes at once
- Hot weather and heavy hydration
- Many children or older guests
- One access point or one bank of units, which causes queues even when the total is adequate
- Few or no handwashing stations, since washing takes time and slows the line
Job sites follow different rules
For construction, the starting point is workforce size and the applicable regulations. See our construction sanitation guide. For long-running sites, also consider the service schedule, since frequent servicing lets one unit support more use than infrequent servicing.
A worked example: a backyard graduation party
For example, imagine a graduation party with 80 guests over about five hours, food served mid-afternoon, and a mix of adults and teenagers. Using the rough heuristic table above as a starting point, that sits between the 50 and 100 guest rows, so two units is a sensible first number to discuss. Now adjust. If there is a toast or a cake-cutting that pulls everyone together, or if the day is hot, a third unit may be worth asking about. If the party is dry and guests also have access to a house bathroom, two may be enough.
The point of the example is the reasoning, not the answer. Start from the table, then ask what makes this particular gathering busier or quieter than average, and tell your provider those details when you call us.
A second example: a fifteen-person job site
For example, a small renovation crew of fifteen with a peak of eighteen when subcontractors overlap should plan around the eighteen, not the fifteen. Peak numbers are the ones that create queues and compliance questions. Work with your safety lead on the count required by your contract and the applicable rules, then think about servicing frequency as a separate lever.
How the count changes by setting
| Setting | What tends to matter most | Planning note |
|---|---|---|
| Job site | Peak headcount, shift length, service schedule | Confirm required counts with your safety lead and contract |
| Festival or fair | Total attendance, alcohol, long stays, multiple entrances | Spread units across the grounds rather than one bank |
| Wedding | Formal clothing, a single big break after dinner, older guests | Consider fewer but more comfortable units, or a trailer |
| Private party | Short duration, access to a house bathroom | Often needs fewer units; ask about guest access to indoor facilities |
Common mistakes when counting
- Using the invitation list rather than the number who actually attend at peak
- Putting every unit in a single spot, so the nearest ones fill and the far ones sit unused
- Forgetting vendors, staff, musicians, and security, who also need restrooms
- Counting only the length of the event and ignoring setup and teardown crews
- Skipping a mid-event service on a long or heavily attended day
- Treating a heuristic table as a guarantee instead of a starting point
Questions to ask any provider
- What unit count do you suggest for my headcount, duration, and alcohol or food plans, and why?
- Does the plan include a mid-event service, and what does it cost?
- Can units be delivered to separate locations on my site?
- What is your plan if turnout is higher than expected on the day?
Do not forget accessibility and handwashing
Include at least one accessible unit for public events, and plan handwashing stations, typically one per restroom cluster and extra near food. Then call us with your headcount and schedule, and we will work through the plan with you.
Published 2026-10-01. This guide is general information, not legal or engineering advice.