Can I try to rephrase the question. How do I know how long to buy stringer wood for my basement stairs? Randy, first figure where you want the stairs to end and mark that on the basement floor. If it can be anywhere, make the run about as long as the rise, then mark the spot on the floor. Now just measure the spot on the floor. Then measure from the first floor to the spot on the basement floor. Then buy the next longer wood length since the 2 x 10's are available in 2 foot increments.
I really suggest that you borrow a book from the library on this if you are not sure how to do it. It's not that it is that difficult, it's that there are some rules of thumb that make the stairs more comfortable to use. Remember to watch you overhead clearances also. You may have to adjust the run so you can get up and down the stairs without bumping your head.