Safety Factor Calculator

Formula

• Factor of safety = Yield strength ÷ Applied stress
• Utilization = Applied stress ÷ Yield strength × 100%

About this calculator

Part of our Mechanical Calculators collection. Beams, bolts, springs, gears, bearings, and core ME calculations.

How it works

Factor of safety equals yield strength divided by applied stress. A value below 1.0 means the part exceeds yield under the assumed load. Stress utilization shows how much of the yield capacity you are using.

Enter your values in the inputs above and click CALCULATE. Results appear on the right without a page reload. No login and no server upload.

Worked example

Steel with 250 MPa yield, 80 MPa applied stress.

1. FoS = 250 ÷ 80 = 3.13
2. Utilization = 80 ÷ 250 × 100 = 32%

Result: Factor of safety 3.13 (pass). The part uses 32% of yield capacity.

When to use

• Quick margin check during preliminary design
• Teaching factor of safety concepts
• Checking if a part is near yield under assumed stress

Limitations

• Uniaxial stress only; no stress concentrations
• Static loading assumed unless you apply your own design factor
• Does not replace code compliance checks

FAQ

What is a good factor of safety?

Static ductile parts often target 1.5 to 2.0. Dynamic or impact loading needs higher margins. Always follow your project code or company standard.

What does fail status mean?

FoS below 1.0 means applied stress exceeds yield under the assumed load. The part would yield in this simplified model.

Yield vs ultimate strength?

This calculator uses yield strength. Ductile design typically limits stress to yield; brittle materials may use ultimate.