The present morphometric analysis represented the actual scientific length-weight relationships (LWRs) for commercially important five fish species namely Salmostoma bacaila, Setipinna phasa, Polynemus paradiseus, Silonia silondia, Chelon parsia from Rupnarayan River in South West Bengal, India. Samples were collected from different fishing centre at Rupnarayan River basin on regular mode of quarterly interval from the year August 2016 to January 2018. LWRs parameters likewise intercept (a ), slope (b) from the formula W= a TLb have been calculated out of total 1190 individual sample under five families. Thus, the LWR parameter b value ranged from 2.89 to 3.13 whereas regression coefficients (r2) range confined within 0.95% to 0.98%. Hence, the current assessment may help concerned to researchers and policy makers for sustainable management and conservation aspects of these commercial fishes available in Rupnarayan River, West Bengal, India.