Know the maximum allowed riser height to determine the rise and run of stairs. For a standard straight run of stairs in a residence, the maximum stair riser height is 7 3/4 inches, and the minimum tread depth is 10 inches. The risers is the vertical part of a step, and a tread is the horizontal part that you walk on. To calculate how many risers are needed, measure the floor-to-floor height in inches, then divide the height by 7 3/4. The result will likely be a fraction, so always round up.