Factor of Safety

Not Reviewed
Equation / Last modified by KurtHeckman on 2017/09/25 15:21
MichaelBartmess.Factor of Safety

This Factor of Safety (FoS) calculator computes the ratio of the tested material strength (S) verses the planned design load (DL).  In this case, it's comparing forces.

INSTRUCTIONS: Choose the preferred units and enter the following:

  • (S)  This is the tested or specified (spec) strength of the material for the force it can support.
  • (DL)  This is the design load for the application of the material.  

Factor of Safety (FoS): The calculator returns the Factor of Safety as a real number.  However, this can be automatically converted to a percentage via the pull-down menu.

General Information

Factor of Safety is an engineering term used to ensure design capacity exceeds actual loads.

The FoS can be defined as the ratio of absolute strength (structural capacity) to actual load.  The value of the FoS may also be specified by law or by  engineering standards. Since the ratio defines the limit beyond which the system will not fail, it is a measure of the reliability of a system's design.

The FoS essentially defines how much stronger the system is than it needs to be to support the intended load.

Generally systems are designed stronger than needed for normal use, with an intent for the safety factor to encompass emergency unexpected conditions.  The greater the FoS, the larger is the safety "cushion" between just supporting design stress and supporting emergency or unnatural forces.