We aim to discover the accuracy of photometric mass ratios (q
ph) determined for eclipsing binary stars, in the case of the system having at least one ‘flat bottom’ as a minimum profile, as well as the accuracy of data used in that sense. Within this context, we present the results of two-dimensional grid search (q – i) for some W UMa-type eclipsing binaries showing total eclipses, based on the high precision photometric data provided by the KEPLER Mission. The radial velocity data obtained for KIC10618253 in this study, enables us to compare both q
ph and the corresponding spectroscopic mass ratio (q
sp) values. The results indicate that the high precision photometric data for overcontact eclipsing binaries showing total eclipses allow us to obtain the photometric mass ratios as accurate as the spectroscopic values.