The current work intends to investigate the quality of selected herbs and create a QbD assisted RP-HPLC method for the simultaneous estimation of gallic acid and rosmarinic acid. According to physicochemical, phytochemical, and toxic contaminant analysis, the quality of crude Terminalia chebula and Ocimum sanctum samples was assessed. The ATP and CQA’s were determined, and then the method was optimized using a 22 factorial design. The tailing factor GA (R1) and theoretical plates GA (R2) were chosen as dependent variables, meanwhile the flow rate (X1) and mobile phase ratio (X2) were chosen as independent variables.