Six methods of determining parabolic expressions of height-diameter relationships have been compared with two other mathematical methods of curve-fitting. It has been shown that short-cut approximations of the least-squares solution of the parabola are accurate; they are useful because of their ease of application and good conformance with the true height-diameter relationship. In this example the short-cut approximation methods have provided more desirable solutions than those secured using Henricksen's semi-logarithmic method, Stoffel's log-log method, H. A. Meyer's exponential solution of the parabola, and Staebler's precise least-squares solution of the parabolic equation with "a" variable. Three short-cut methods for calculating parabolic curves have been illustrated with data from the Campus Forest of the University of British Columbia. Special uses of the parabolic relationship have been described. Construction of site-class volume tables has been demonstrated with data for a number of commercial tree species in the Arrow Lakes District of British Columbia. The short-cut methods of determining parabolic height-diameter relationships have so many advantages that they are recommended for general use in forest inventory and for permanent plot studies.