The ratio of resistance or strength of a material or structure to the applied load. In geotechnical engineering, it refers to the ratio of the available shear strength to shear stress on the critical failure surface.

The ratio of ultimate load to greatest allowable working-load. This term is getting out of favor among engineers, as its use has been somewhat abused. There is no such thing as a factor of safety for a well-proportioned bridge, for each member should have an intensity of working-stress proportionate to the character and amount of work which it has to perform.

The ratio of the maximum strength of a piece of material or a part to the probably maximum load to be applied to it. If a maximum of 2,000 pounds can be tolerated, a load of 500 pounds will have a 4 to one factor of safety.

In the wire rope industry, this term was originally used to express the ratio of nominal strength to the total working load. The term is no longer used since it implies a permanent existence for this ratio when, in actuality, the rope strength begins to reduce the moment it is placed in service. See DESIGN FACTOR.

Ratio of breaking strength of a wire rope to total rope stress Independent Wire Rope Core - Wire rope used as the core of a larger rope

A design factor such that where multiplied by the allowed working stress for a given material it will give a product equivalent to the ultimate strength of that material. The foregoing defines "factor of safety" as ordinarily used. Strictly speaking and especially for elastic materials this dentition applies only to the "nominal factor of safety." The real factor of safety for design work involving elastic materials is that factor which if multiplied by the allowed working stress will be equal to the stress required to strain the material to its elastic limit. If the nominal factor of safety is used in any case, the real factor of safety for the case in hand is smaller in proportion as the elastic limit of the material is lower than the ultimate strength. For design in such materials as wood, cast iron in compression, and the like, the distinction between nominal and real factor of safety is non-existent.

The ratio of ultimate strength to the working stress of a material.

Determined by dividing the stress at which a body will collapse by the maximum stress it will be called upon to bear

Ratio of the ultimate strength to the working or allowable loads.

Factor of safety (FoS), is a the percentage of capability over the requirements that a structure has. It is commonly confused as being a safety factor which is a multiplier applied to the calculated maximum load (force, torque, bending moment or a combination) to which a component or assembly will be subjected. A safety factor is applied to a requirement, whereas a Factor of Safety is calculated after the fact.