The product mix problem is one of the salient issues faced by SMMEs. The study aims to establish a product mix optimisation model to address the problem. To achieve this goal, QM for Windows software is deployed to ascertain an optimal production level to maximise profit for NAYO Aluminum Company fabricators of aluminium products in Enugu (Eastern Nigeria). This software uses raw material and production requirements data to perform optimisation calculations. The analysis includes (1) the number of windows and doors to be produced using the available resources to maximise total income, (2) total costs of production, and (3) gross income. The findings indicate unused resource levels, which helps to manage input resource procurement and minimise waste. The analysis result using QM for Windows, after linear and integer programming, shows an optimal production: 28 aluminium doors and 2 casements (P₁ =0; P₂ =2; P₃ =28, P₄ =0) to make the highest income of 119720.00 Naira (Max Z = 1720P₁ + 4000P₂ + 3990P₃ + 2970P₄). This application can improve productivity, inventory management and company profitability.