Factor of Safety Calculator Formula
Understand the math behind the factor of safety calculator. Each variable explained with a worked example.
Formulas Used
Factor of Safety
fos = material_strength / applied_stressUtilization Ratio
utilization = applied_stress / material_strength * 100Variables
| Variable | Description | Default |
|---|---|---|
material_strength | Material Strength / Ultimate Load(MPa) | 250 |
applied_stress | Applied Stress / Working Load(MPa) | 150 |
How It Works
Factor of Safety (FoS)
The factor of safety expresses how much stronger a system is than it needs to be.
Formula
FoS = Strength / Applied Load
A FoS of 1.0 means the member is at its exact limit. Values above 1.0 provide a safety margin. Typical minimum factors: buildings 1.5-2.0, bridges 2.0-3.0, aircraft 1.25-1.5, pressure vessels 3.0-4.0.
Worked Example
A steel member with 250 MPa yield strength under 150 MPa stress.
material_strength = 250applied_stress = 150
- 01FoS = 250 / 150 = 1.67
- 02Utilization = 150 / 250 = 60%
- 03The member has a 67% safety margin above the working load.
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Open Factor of Safety Calculator