I was searching for some formula or something to help me figure out the cut for stairs. I found this site and you offering advice. I am building simple entry stairs to a platform, and then inside. I believe it is 3'2" and there are now 3 existing treads, and 4 rise. I want to keep it that way. Basically I am replacing the old. So what I need is the formula or something to help me figure it out.