The single marking and recapture method is one of the methods commonly used to estimate fish population size. There are four formulae in this method, two of which are suggested by Bailey (1951), one by Chapman (1952) and the last by Ricker (1975). For this reason, in the current study, firstly, one of Bailey's formulae (1951) was examined mathematically and statistically. Secondly, numerical data obtained from Duzgunes (1985) were used and his results from Mogan Lake were compared. As a result, population size estimation of the carp (Cyprinus carpio L.) in this lake was calculated using the four formulae as $9716 \pm 360$, $9381 \pm 3354$ (Bailey, 1951), $9409 \pm 3218$ (Chapman, 1952) and $9410 \pm 3364$ (Ricker, 1975). It is suggested that as the confidence interval is narrower in the formula proposed by Chapman (1952) than the other formulae, the results obtained using this formula are more reliable.