Restroom Trailer Size Calculator

The baseline is the industry's golden rule — 1 stall per 50 guests for a 4–6 hour event — adjusted by event type using Stahla's published formulas: ceremony-only crowds need about 1 stall per 100 guests, cocktail receptions 1 per 50, and full dinner receptions or festivals 1 per 40. We then add 20% when alcohol is served (bar events run 20–40% higher restroom usage) and another 20% for events running past 6 hours, and always round up.

The stall count maps to a trailer size using guest-count capacity charts published by rental providers: roughly 75–150 guests for a 2-stall, 150–225 for a 3-stall, 200–300 for a 4-stall, 350–450 for a 6-stall, 500–600 for an 8-stall, and 700+ for a 10-stall. We treat the 2-stall as the practical minimum — single-stall trailers are rare in most markets — and always size up rather than down.

Job sites use different math: OSHA 29 CFR 1926.51 Table D-1 requires 1 toilet for crews up to 20 workers, then 1 toilet seat plus 1 urinal per 40 workers. The ADA guidance (at least 5% accessible stalls, minimum 1, for public events) comes from accessibility compliance guides for portable sanitation. This is a planning tool, not a compliance ruling — local providers confirm the final configuration for your venue and jurisdiction.

Estimates only — independent local providers quote their own pricing. Data last reviewed 2026-07.