This document aims to standardise metrics for measuring progress on reusable packaging systems. It outlines a framework to support public and private sector stakeholders, including corporations, policymakers, and non-profits, in scaling reuse practices to combat plastic waste. Key areas covered include definitions and parameters for reuse, two prioritised metrics to assess progress (share of reusable product volume and reuse effectiveness), and detailed measurement approaches. The report emphasises the need for harmonisation in measurement to facilitate transparency, build consumer trust, and drive systemic change towards reducing single-use plastic and promoting a circular economy​.