Warning: This part here is for interior design nerds only (hehe)
So, after watching a youtube video many *many times to figure this stair calculation thing out.. this is what I have come up with (This example is from the video) here is the link: http://www.youtube.com/watch?v=531UPCjZTm0
Step 1: Total rise needed (this is the distance/height from the floor your stairs are starting on to the floor up where your stairs are going to): 109.75"(about 9')
For residential stairs risers are about 7" high and the run (tread) depth is about 10"
Step 2: 109.75 divided by 7"= 15.68 stairs, so you will need 15-16 stairs
109.75 divided by 15= 7.32" OR 109.75 divided by 16= 6.86" To make a fraction (or number that can be measured on a measuring tape) take the .86 and mult. by 16 which= 13.76 rounded up to 14/16th's or 7/8ths
Step 3: SO 6 7/8" rise over a 10" run
What this means: There will be 16 stairs that are 6 7/8" high and 15 treads that are 10" deep (You always need 1 more riser then you do treads).
Boring post? I think not :)