The purpose of this study is to explore a proposed approach to quantitatively characterize a threedimensional (3-D) fit. A 3-D body scanning technique was applied to capture the contour of nude and clothed manikin. The mesh model formed from nude and clothed scan by Rapidform software was aligned, superimposed and sectioned. From the neck to cuff, total 72 horizontal sections with equal interval of 2 cm were developed. The air gap size and distribution of overall and local body surface were analyzed. The total air volume was also calculated. Fit analysis was conducted on several protective clothing. The effect of fabric properties on air gap distribution was explored. The results indicated that average air gap of the fit clothing is around 25~30 mm and the overall air gap distribution is similar. The air gap showed uneven distribution over the body and it related to the body geometry and fabric properties. Larger size of air gap in legs and abdomen was observed. The air gap in chest, pelvis and arms, however, is minimal. The air gap over convex area is smaller than that of concave area. Coverall made of stiff fabric provided large air gap size. The research finding provides a technical base for clothing engineer to understand the overall fit associated with protection, thermal and movement comfort.