This study investigates the relationship between specific gravity and the flexural properties of twelve tropical wood species with specific gravities ranging from 0.39 to 0.67. An experimental approach was employed to determine three-point bending properties under air-dry or normal moisture conditions in accordance with ASTM D143-22. Bending load–deflection curves were obtained from flexural tests, and regression analysis was performed to develop empirical equations describing the relationships between specific gravity and bending properties. The results demonstrate a significant correlation between specific gravity and wood bending strength, particularly at the proportional limit load and ultimate limit load (modulus of rupture). The consistently low p-values of the developed equations indicate that specific gravity has a statistically significant effect on the flexural mechanical properties of wood. Although the proposed models do not fully account for the inherent variability of wood arising from factors such as tree age, grain orientation, temperature, moisture content, and other natural variations, they effectively describe the overall trends observed in the experimental data. Bending strength can support the design of flexural members using the Load and Resistance Factor Design method, while modulus of rupture can be applied in designs based on the Allowable Stress Design method. The developed empirical equations provide useful predictive relationships between specific gravity and flexural properties and may assist engineers and researchers during the early stages of timber grading. A limitation of this study is the variation in grain angle, which may have contributed to the observed variability in bending strength and modulus of rupture.
