In this study, the effects of methanol-to-oil molar ratio, catalyst amount and reaction time on the transesterification of waste cooking oil (WCO) to biodiesel were investigated. Methanol with calcium oxide as a heterogeneous catalyst was used for the transesterification process at a temperature of 60oC and 3000 rpm stirring speed. Response surface methodology (RSM) with central composite rotable design (CCRD) was used at five levels of oil-to-methanol molar ratio (9: 1–14: 1), catalyst (1-5%) and reaction time (30–90 min) as independent variables and WCO biodiesel yield as dependent variable (response). A statistically significant (P< 0.0001) second-order quadratic polynomial regression model with a coefficient of determination, R (= 0.9964) was obtained for biodiesel production (using Design-Expert Statistical program (v. 6.0. 8)) and verification experiment confirmed the validity of the predicted model. Numerical optimization technique based on desirability function was carried out to optimize the WCO conversion to biodiesel. The optimum combinations for transesterification to achieve a predicted maximum biodiesel yield of 94.15 percent were found to be: oil-to-methanol molar ratio, 9.14: 1; catalyst amount, 3.49% and reaction time, 60.49 min. At this optimum condition, the observed biodiesel yield was found to be 94.10 percent. In addition, the fuel