Safety First: How to calculate the Factor of Safety

In Mechanical Design there is a very important concept that allows engineers to design safe components. It literally saves your life every time you take a flight, cross a bridge or climb a mountain.

Beto is relaxed because he knows that his climbing equipment is safe

It's known as the Factor of Safety and it's defined as follows:

where:

• FS: Factor of Safety
• Strength: Mechanical Strength of the component (in stress units)
• Stress_max: Maximum stress allowed in the component

The objective of this formula is to find Stress_max. This is the stress that shouldn't be surpassed in your design.

In order to find Stress_max you need to know the other two variables:

• FS
• Strength 

You can use the following table to get them:

Factor of Safety: Table

Once you have calculated the Factor of Safety (FS) and you have the value of the Strength, you will get Stress_max using the formula. Now you have the value of stress that sets a limit for your design.

In conclusion, the Factor of Safety is a very important concept in Mechanical Engineering because it allows engineers to design safe products. It can also help you make efficient designs by avoiding a Factor of Safety larger than necessary.

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