Basically, if your production rate is 2800 sq. ft. per hour, an 8 hour shift will allow coverage of 22,400 sq. ft. and a 100,000 sq. ft. facility will need 4.5 FTEs to do the cleaning.
The problem with this simplistic approach is obvious. No one knows if that rate works for your people in your facility for all tasks, and under all circumstances. Chances are very good it does not.
You can ask around at...