There is no single event ratio that fits every rental. Send peak users, hours, existing facilities, and the layout. For construction, use the applicable OSHA fixture baseline and plan cleaning separately.
Start with the busiest period
Give Harold Rental Works the greatest number of people who will be onsite together, not just the total visiting over a week. Include workers on overlapping shifts or guests, staff, and vendors at an event. Note bathrooms people can actually use during the same hours. A single headcount is a starting detail, not a complete rental specification.
Construction has a specific baseline
OSHA 1926.51 Table D-1 sets construction toilet minimums: one facility for 20 or fewer employees; one toilet seat and one urinal per 40 workers in the next tier; and one seat and one urinal per 50 workers for 200 or more. For 60 workers under the one-per-40 ratio, round 1.5 up to two seats and two urinals. The responsible employer must review applicability, exceptions, equipment, and sanitary conditions.
Events need their own usage plan
A four-hour reception and an all-day public program can have the same guest count but different use. Share public hours, food and drinks, separate activity areas, and whether permanent restrooms remain open. Discuss extra equipment and service together. The customer call requesting 12 toilets and three washing stations described one festival; it is not a universal guest-to-toilet formula.
Plan accessible groups individually
The Access Board guide requires at least 5% accessible portable units in each covered cluster, with applicable exceptions. A covered group of ten needs at least one; thirty needs at least two. Confirm the documented model and the usable approach. Combining all units across a site into one total can overlook the requirements of separate groups.
Send a layout with the quantity request
For a Longview outdoor program, show the restroom groups, washing, walking routes, and supplier entrance on the event layout. Check the city and venue process separately. For a worksite, show changing phases and service access. The final quote should identify quantity, equipment features, cleaning frequency, and a ready-by date.