Divide your height from floor to floor by the number 7. What ever the answer is, say 13.73, You can't have 13.73 risers, so, take that number, 13, because that is the number of risers you will have and then divide your height by 13. it'll come out something like 7.25 or whatever it works out to be. this will be your riser height. I personally like an 11" tread, it walks nicely with a riser in the 7" range or there abouts. If you've got 13 risers you'll also have 13 treads. 13" x 11" = 143. You're answer wiill be different but you can use this example to figure out what you'll have. If you're tight on space you may have to build a landing and turn the steps another direction. build your landing on some multiple of the riser height that you've figured out beforehand. sounds complicated but it's really not.