This paper addresses the challenge of accurately measuring the E-Service Quality (ESQ) of app-based travel portals by using a structured framework of linguistic and mathematical variables. The approach allows for the evaluation and improvement of key performance indicators through fuzzy aggregation, providing a quantitative understanding of service quality in dynamic environments. The proposed method evaluates the system's state by analysing the parametric values of its sub components, which define the system at any given time. We identify three primary factors crucial for assessing ESQ: the state change required relative to the current system state and the relative significance of tasks. The paper elaborates on three critical variables: the significance of a factor (Si), its observed level (Li), and the contribution of the factor (Delta i) towards ESQ. These variables are assessed using fuzzy aggregation, converting linguistic inputs into crisp numeric outputs, thereby quantifying the impact of each factor. The methodology provides a structured and flexible approach to gauge and improve the performance of travel portals by focusing on key performance indicators and their respective weights.