  The number of stellar angular diameter measurements has greatly increased
over the past few years due to innovations and developments in the field of
long baseline optical interferometry (LBOI). We use a collection of
high-precision angular diameter measurements for nearby, main-sequence stars to
develop empirical relations that allow the prediction of stellar angular sizes
as a function of observed photometric color. These relations are presented for
a combination of 48 broad-band color indices. We empirically show for the first
time a dependence on metallicity to these relations using Johnson $(B-V)$ and
Sloan $(g-r)$ colors. Our relations are capable of predicting diameters with a
random error of less than 5% and represent the most robust and empirical
determinations to stellar angular sizes to date.
