# Factor of Safety

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Factor of safety, abbreviated as FS, also called safety factor, a dimensionless number, is the ability of a system's structural capacity to be usable beyond it's expected or acrual loads.

## factor of safety formula

$$\large{ FS = \frac {UTS}{R} }$$
Symbol English Metric
$$\large{ FS }$$ = factor of safety $$\large{ dimensionless }$$
$$\large{ R }$$ = applied stress $$\large{ \frac{lbf}{in^2} }$$ $$\large{ Pa }$$
$$\large{ UTS }$$ = ultimate tensile stress $$\large{ \frac{lbf}{in^2} }$$ $$\large{ Pa }$$