The rule of thumb
Event restroom companies size with a simple rule: roughly one stall for every 50 guests over a four to six hour event. For a full dinner reception that runs into the night, some sizing guides divide the guest count by 40 instead, and add about 20 percent more capacity when alcohol is served.
Source: Stahla, "What size of restroom trailer do I need?"
| Guests | Stalls by the rule of thumb | What that usually means |
|---|---|---|
| Up to 100 | 2 | One three-stall trailer, with room to spare |
| 150 | 3 | One three-stall trailer |
| 200 | 4 | One three-stall trailer is workable for most weddings; an attendant helps |
| 250 and up | 5 or more | Plan a second unit, or talk to us about the run of show |
Sizing guides put a three-stall trailer at roughly 150 to 225 guests for a four to six hour event. In practice most weddings of up to about 200 guests are comfortable with one.
What pushes the number up
- A long day. Ceremony, cocktails, dinner, and dancing can run eight hours or more. The longer guests are there, the more capacity you need.
- An open bar. Guests visit more often as the night goes on. Plan for about 20 percent more.
- The guest mix. A crowd that is mostly women will queue sooner than the average.
- Peak moments. Right after the ceremony and after dinner are the rush hours. Capacity is about those minutes, not the average.
What brings it down
- A shorter event, like a ceremony and cocktail reception.
- An attendant. Someone keeping the trailer clean and stocked keeps the line moving, which matters more as the guest count climbs.
- Other washrooms on site that guests can actually use, such as a venue building with real plumbing.
Do not count on the house
At an acreage or a family property, it is tempting to count the house washroom. A household septic system and one bathroom are not built for a wedding crowd, and a line through someone's kitchen is not the evening anyone pictured. Treat the house as a backup, not the plan.
Not sure where your wedding lands? Send your guest count, the rough timeline, and whether there is a bar on the check-your-date form. We will tell you straight whether one trailer covers it.