Reader Question: How many toilets is enough?

A version of a question I'm commonly asked by readers:

Question:
I am planning on having my wedding ceremony and reception in my parent's backyard.  I was wondering if you have any advice on bathrooms.  We are planning on having about 150 guests and my parents only have 1 restroom. Rather than having all the guests go all over the house looking for a bathroom, we were wondering if you had any suggestions or if 1 bathroom would suffice.

My answer:
We had this debate as well. My parent's bathroom is sort of tempermental so we ended up renting a toilet.  It actually wasn't gross at all (it was the rental company's special "wedding toilet") and one was plenty for the 100 guests we had.  I was just at another wedding that had around 120 guests and their 1 toilet was a lot busier than ours seemed, but the line was never too long (maybe 2 people at most). I'd say you could probably get by with one if you trust your plumbing!