The following is a basic formula providing for the most efficient arrangement with optimal overall sightlines.
d is the distance from the spectator’s eye to the focal point on the field,
t is the tread depth,
r is the riser height,
e is the elevation of the spectator’s eye above the focal point and
c is the vertical distance between the sightline and the eye of the spectator in the preceding row.
This equation is normally solved for r, to determine the distance by which each tread should be elevated over the preceding tread. The formula dictates that riser height will increase incrementally with greater distance form the focal point. This results in the parabolic, bowl shaped, upward curve for each level of the stadium. The formula is simple, but its application requires judgment and consideration of any special factors resulting from the construction requirements and the unique aspects of each stadium design problem.