Factors to consider in your calculation:

1.- Determine the total time the restrooms should be available.

• Under normal conditions, most people will use sanitation facilities once every 4 hours. ​

2.- Determine how many people will attend

• If you'll need the restrooms for multiple days then use the longest day and the peak attendance expected as a reference.
  
  

3.- If beverages or alcohol will be served add 15% to 20% more restrooms.

4.- If there's a higher ratio of women-to-men-attending,  add 15% to 20%

5.- Add one handicap restroom per 20 standard restrooms, or a minimum of one for events open to the public.

6.- Adequate hand-washing should also be provided with restrooms in all food service areas.

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