Abstract This study refines the Gibson-Ashby model to predict the mechanical properties of functionally graded (FG) honeycombs with random irregularities. By integrating correction factors, the model accommodates variations in aspect ratio and structural irregularities across hexagonal, triangular, and square honeycomb micro-architectures. The study updates analytical expressions to correlate the relative elastic modulus with relative density for graded configurations. These enhancements are calibrated through analytical derivations and finite element (FE) simulations, covering a wide array of irregular FG honeycomb designs. Validations are conducted via FE simulations and experimental tests on 3D-printed samples. A dual homogenization approach effectively translates microstructural variations into macroscopic property predictions, confirming the model's applicability to diverse configurations. The refined Gibson-Ashby model demonstrates high accuracy in relating relative density to elastic modulus in graded and irregular honeycombs. This analytical framework offers a valuable tool for designing optimized FG honeycomb structures across various geometric variations.