What is the formula to figure stair stringers?

Question:I used to know the answer to this, but i've been out of the construction business for awhile.

Answers:
What, the rule of 18? The ideal run is 11, and a 7 inch rise. As the stairs get steeper, the run decreases, and the rise increases. Codes vary regarding how far you can stray either way, and there are special requirements for steps with a low rise and a long run.