  Reliable prediction of stellar diameters, particularly angular diameters, is
a useful and necessary tool for the increasing number of milliarcsecond
resolution studies being carried out in the astronomical community. A new and
accurate technique of predicting angular sizes is presented for main sequence
stars, giant and supergiant stars, and for more evolved sources such as carbon
stars and Mira variables. This technique uses observed $K$ and either $V$ or
$B$ broad-band photometry to predict V=0 or B=0 zero magnitude angular sizes,
which are then readily scaled to the apparent angular sizes with the $V$ or $B$
photometry. The spread in the relationship is 2.2% for main sequence stars; for
giant and supergiant stars, 11-12%; and for evolved sources, results are at the
20-26% level. Compared to other simple predictions of angular size, such as
linear radius-distance methods or black-body estimates, zero magnitude angular
size predictions can provide apparent angular sizes with errors that are 2 to 5
times smaller.
