How Many Sentences are in a Paragraph?

This seems like one of the basic rules of grammar. However, as an online writer I find it's often one of the most disputed rules. Every company has different rules about what a paragraph is. It's not just like looking up how to get rid of acne where you can get a definite answer. I remember in my elementary school it was 4-6. Other people will argue it's 3-8. This is one of the most difficult parts of writing for me because I love 15 sentence paragraphs. I really love this answer that says that it can be as long as it needs to be to get an idea across, even if it takes 100 sentences. Really that's what a paragraph is but everyone has their own stipulations on it.