How much will indoor/outdoor carpet stretch?

All depends on the quality of the original product.

It depends on the company who made the carpet. You could call a few companies that sell carpet and ask them.

Hello William Lynn ;)

I have searched every place I can think of, reading articles / scanning articles, for an hour now, and all I have learned is that indoor-outdoor carpeting does have some stretch to it, just as all carpeting does, but how much stretch is something that just isn't stated in anything I have read. The closest thing that came to it said that when measuring the size of your room for laying the carpet, "add two inches" (to the room measurement? to the carpeting? it didn't say nor did it explain why). I'm so sorry I couldn't find the information you were asking about, both for you and for me, because now this is going to be on my mind all day. I love to learn things and when I set out to know something it really bothers me if I can't find an answer. All I can say at this point William Lynn is Good Luck, and thank you for asking HOMETALK for an answer to how much will indoor-outdoor carpet stretch. I wish I knew.

Maybe a couple of inches either way?

it don't stretch much at all if any.