Purpose ‐ This paper seeks to propose a methodology to measure the extent of collaboration between apparel retailers and manufacturers in the apparel retail industry in India. Design/methodology/approach ‐ The proposed model for measuring collaboration considers variables like top management commitment, information sharing, trust among supply chain partners, long-term relationships and risk and reward sharing. Level of collaboration is measured using graph theory. Findings ‐ The survey results confirmed the validity of the proposed collaboration index for measuring collaboration. The findings also show that the collaboration index is positively associated with operational performance. Research limitations/implications ‐ Future research could consider larger sample sizes and cover other industrial sectors. Practical implications ‐ Supply chain partners will be able to measure the extent of their collaboration and seek improvement in their performance. This approach helps to compare organizations in terms of their collaboration capability. Originality/value ‐ This paper contributes to the literature by introducing an index for measuring the extent of supply chain collaboration. This measure can be used by any participant (member) in a supply chain to determine the level of collaboration and seek improvement.