Toilet formula
It's a good idea to provide one toilet for every 75 registrants (that includes walkers). If your race is longer than 10k, or if the majority of entrants travel a long distance to the race, provide one toilet for every 50 registrants, since more people will use them - and more often.
By the way, here's a toilet calculator we found for outdoor events like fairs and carnivals. It's not for races, but you still may find it interesting.
Posted in Course issues