How this calculator works
The calculator divides total rise by your target riser height and rounds up to a whole number of risers. It then recalculates the actual riser height by dividing total rise by the whole riser count. For a typical straight stair, tread count is usually one less than riser count, and total run is tread count multiplied by tread depth plus any landing length.
Example: 108 inches of total rise with a 7 inch target riser rounds to 16 risers. The actual riser height becomes 6.75 inches. With 10 inch treads, 15 treads create a 150 inch run before any landing.