Factor of Safety Calculator

Enter the total maximum stress and the current working stress into the calculator to determine the factor of safety.

Factor of Safety Formula

The following formula is used to calculate a factor of safety.

FoS = MS / WS

  • Where FoS is the factor of safety
  • MS is the maximum stress the object can withstand
  • WS is the working stress the structure is rated for or used at

Factor of Safety Definition

A factor of safety is a measure of the amount of extra strength is designed into a structure to hold stress in excess of the expected stress in order to have an increase level of safety.

Factor of Safety Example

How to calculate the safety factor?

  1. First, determine the maximum stress.

    Measure the maximum stress of the object can withstand.

  2. Next, determine the working stress.

    Measure the working stress the structure is rated for.

  3. Finally, calculate the factor of safety

    Calculate the factor of safety using the formula above.


What is a factor of safety?

A factor of safety is a term used in engineering to describe the relationship between the maximum stress a structure and hold and the stress the structure is designed to be used at. In other words, the larger the factor of safety the lower the working stress compared to the maximum stress.

What is a good factor of safety?

This is entirely dependent on the application or structure. For less critical components and structures factors of safety of 2 are often used, but when human lives depend on the function of a structure factors of safety of 3+ are usually used.

factor of safety calculator
factor of safety formula