Several studies have appeared in the literature describing methods for deriving stellar continuum fluxes as simple functions of Johnson color indices. In previous papers, we have used similar relations to derive Ca II H & K line core fluxes for dwarf stars on Lowell Observatory's Solar-Stellar Spectrograph (SSS) program. Our desire is to present our data, and complementary data from the Mt. Wilson and National Solar Observatory stellar and solar programs, in terms of physical fluxes. However, our existing relations break down for mid-K and later stars and for giant stars, which form an important element of our target list. In this work I have used a broader range of spectrophotometry and angular diameters than in our previous work to derive empirical flux scales for spectral types A to early M, luminosity classes I to V, and for four color indices, Johnson B-V, V-R, R-I, and Stromgren b-y. In this paper I describe the methods I used and present the derived flux scales. I compare the results with those from earlier studies and present examples of the use of the flux scales. The data and results are available on the World Wide Web home page. Access <http://www.lowell.edu>, select "Lowell staff", and select the author's home page.