Purpose <p>This study aims to develop a comprehensive and operational methodology for quantifying the environmental impacts and the avoided emissions credit-allocation in product reuse scenarios. It addresses a critical gap in conventional life cycle assessment (LCA) methodologies, which often fail to fully account for the benefits of reuse, particularly in the allocation of environmental burdens and benefits across product lifespans.</p> Methods <p>The proposed approach introduces a utility-based framework that traces environmental impacts and credits across virgin material production, refurbishment, use, and end-of-life stages. It integrates structured allocation rules using donor and receiver utility functions to reflect functional equivalence and actual reuse conditions. The methodology is benchmarked against established LCA standards (e.g., EN 15804 + A2, ISO 14044) and common allocation models (e.g., cut-off, 100:0, 50:50). Applicability is demonstrated using real-world case studies involving building products.</p> Results <p>The framework enables a transparent, fair, and traceable accounting of emissions by allocating avoided emission credits to donors (first-life users) for extending the product service life and for reducing the demand for virgin resources. Receivers (second-life users) benefit from the reduced embodied carbon of reused products. The case studies validate the method’s robustness and show measurable greenhouse gas reduction under realistic scenarios when products are reused.</p> Conclusions <p>This methodology offers a scalable, practical, and verifiable approach to quantify product reuse benefits. It fosters stakeholder engagement by rewarding both donors and receivers, supports accurate carbon accounting in line with climate goals, and enables a better integration of reuse scenarios into mainstream life cycle assessment practices. Ultimately, it contributes to the advancement of circular construction models and sustainability-driven procurement.</p>