How many porta potties does a job site need?

For a construction crew: 1 toilet for up to 20 workers, then 1 seat and 1 urinal per 40 workers up to 199, then 1 per 50. That is OSHA 1926.51 Table D-1. At weekly service, plan on 1 unit per 10 workers (ANSI Z4.3) or the units are full by Thursday.

Workers on site	Minimum toilets (OSHA 1926.51 Table D-1)	At weekly service (ANSI Z4.3)
Up to 20	1 toilet	1 per 10 workers
20 to 199	1 seat + 1 urinal per 40	1 per 10 workers
200 or more	1 per 50	1 per 10 workers

Worked examples

8 workers, 3 months: OSHA minimum 1. Order 1 standard + 1 handwash. About $188 to $310 per 28 days.
20 workers: OSHA minimum 1. At weekly service, 2 standard + 1 handwash. About $326 to $520.
45 workers: OSHA minimum 2 seats + 2 urinals. At weekly service, 5 units + 2 handwash. About $790 to $1,250.
100 workers: OSHA minimum 3 seats + 3 urinals. At weekly service, 10 units + 4 handwash. About $1,580 to $2,500.

Events are a different table

For a party or festival the usual planning number is 1 unit per 50 to 100 guests for 4 hours, more if alcohol is served. This site is for job sites; event companies price those directly.

The rule that catches people

An unsanitary unit does not count toward the minimum (OSHA interpretation letter, May 17 2006). One unit for 20 workers that gets pumped once a week is a write-up waiting to happen in August. Handwashing with soap and towels is required separately under 1926.51(f).

Houses

Production builders commonly place 1 unit per 4 houses under construction and move it as crews move. A single custom home runs 1 unit, 2 if the crew tops 10.