Factor of safety, also known as Safety Factor, is a multiplier applied to the calculated maximum stress to which a component will be subjected. Typically, for components whose failure could result in substantial financial loss, or serious injury or death, a safety factor of at least four (4) is used. Non-critical components generally have a safety factor of two (2). Safety factors are needed to account for imperfections in materials, flaws in assembly, material degradation, and unexpected stresses.