<p>Web accessibility is a fundamental requirement for inclusive higher education, yet it remains insufficiently represented in institutional evaluation frameworks, which often rely on raw counts of accessibility issues and provide limited guidance for prioritisation. To address this limitation, this study proposes an Accessibility Index (AIx), a composite score ranging from 0 to 100 that summarises the accessibility performance of university websites by integrating multiple categories of accessibility issues, including errors, contrast problems, and structural elements, into a single interpretable measure. The index assigns differential importance to these issue types according to their likely impact on users with disabilities, drawing on both accessibility practice and data-driven analysis. Using automated metrics derived from the WAVE tool, the study compares alternative weighting approaches and evaluates the robustness of the resulting rankings under changing assumptions. The results show that the rankings remain highly stable across weighting scenarios, with contrast-related issues and code-level errors emerging as the dominant contributors to accessibility performance. In addition, accessibility scores exhibit little correspondence with conventional institutional rankings, indicating that accessibility constitutes a distinct dimension of digital quality. Overall, the proposed AIx offers a transparent and practically useful framework for benchmarking accessibility and supporting more targeted remediation in higher education.</p>