Describe the busiest period
For an event, explain the largest group expected together and whether guests arrive in separate sessions. Include vendors and staff working before opening or after closing. For a worksite, include subcontractors and overlapping shifts instead of only the main payroll.
Count usable existing facilities
Identify permanent restrooms that users are allowed to access during the whole period of need. Note closures, restricted keys or a location too far from a separate activity area. Do not count a facility simply because it exists on a property map.
Treat accessibility and washing as their own requirements
Discuss the relevant accessible facilities and routes, and include handwashing provision. These are not interchangeable with increasing the number of standard cabins. The organiser or employer remains responsible for reviewing the requirements that apply to the actual use.
Review quantity together with servicing
Describe long operating days, repeated sessions or changing demand so the team can discuss a suitable service arrangement. This page deliberately avoids a universal numerical ratio: an unchecked rule could be wrong for your occasion. Ask the provider to explain its proposed quantity and review assumptions before accepting it.