Factor of Safety Calculator — Formula
## 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.
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.
Exemplo Resolvido
A steel member with 250 MPa yield strength under 150 MPa stress.
- FoS = 250 / 150 = 1.67
- Utilization = 150 / 250 = 60%
- The member has a 67% safety margin above the working load.