Disassembly complexity is the extent to which individual parts or subassemblies have geometric and physical attributes causing difficulties or problems in handling and removal. Managing the complexity of disassembly at the design phase has positive effects on End of Life disassembly. This work explores and improves an existing solution that quantifies the disassembly complexity of products, allowing for an assessment since the very early stage of design. The index becomes applicable to any kind of product and results comparable. The present paper integrates the aspect of the evaluation of the complexity of manipulation with the model of the quantitative evaluation of the complexity of disassembly. The complexity index proposed by Soh et al., based on the average handling and disassembly complexity indexes was reviewed and updated. Calculation is done considering both the liaison and the part or subset. The main criticalities (i.e., low sensitivity on similar cases, limited parts dimensions) are overcome. The case study provides an application of the new index and shows the main improvements from the existing one. The designer is thus provided with consistent quantitative feedback. Future works will strengthen the values of the index with the support of tools to quantify muscle strain.