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 50 | 1 | One two-stall trailer, with room to spare |
| 75 | 2 | One two-stall trailer |
| 100 | 2 | One two-stall trailer; for a long night with a bar, send us the timeline |
| 125 | 3 | One stall more than a two-stall trailer; talk to us about the plan |
| 150 | 3 | One stall more than a two-stall trailer; talk to us about the plan |
| 175 | 4 | Two stalls more than a two-stall trailer; plan additional washrooms |
| 200 and up | 4 or more | Plan additional washrooms; talk to us about the run of show |
By that rule, our two private rooms comfortably cover most weddings up to about 100 guests over a four to six hour event. The length of the evening and the bar decide where your wedding lands. Bigger guest list? Send your count and timeline and we will talk it through, straight.
How many bathrooms for a 150-guest outdoor wedding?
Three stalls by the one-per-50 rule. For a full dinner reception that runs into the night, dividing the guest count by 40 gives four, and an open bar adds about 20 percent on top. At an outdoor wedding with no venue washrooms, every one of those has to be brought in. Our two-stall trailer covers two of them, so at 150 guests it works alongside other washrooms on site rather than alone.
What pushes the number up
- A long day. Ceremony, cocktails, dinner, and dancing can run eight hours or more, and longer means more capacity.
- 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 family property, it is tempting to count the house washroom. But one bathroom and a household septic system are not built for a wedding crowd, and nobody pictured a line through the kitchen. 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.