In this study, a novel estimating equation based on the WES2808 standard was proposed to predict fracture toughness through the transition temperature of Charpy impact toughness and CTOD (Crack Tip Opening Displacement) fracture toughness. This equation was specifically developed for 460MPa class H-section steel materials used in marine structures, including the base material (BM), heat-affected zone (HAZ), and weld metal (WM). The experimental results confirmed that the proposed estimation equation accurately predicted the fracture toughness across these different material regions. These findings demonstrate the reliability and applicability of the proposed equation in estimated fracture toughness for marine structure materials, thereby contributing to improved safety and performance in harsh environmental conditions.