比强度是材料的强度（断开时单位面积所受的力）除以其密度。又被称为强度－重量比。比强度的国际单位为(N/m2)/(kg/m)或N·m/kg。

The specific strength is a material's strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio. In fiber or textile applications, tenacity is the usual measure of specific strength. The SI unit for specific strength is Pa m/kg, or N·m/kg, which is dimensionally equivalent to m/s, though the latter form is rarely used.