根据不锈钢管的才子、外径及壁厚计算其每米理论重量，理论外表面积，理论内表面积的小工具。主要供非专业土木建筑人士使用。(A small tool for calculating the theoretical weight per meter, theoretical surface area, and theoretical surface area according to the talent, diameter and wall thickness of the stainless ste