There are two separate definitions for the margin of safety so care is needed to determine which is being used for a given application.
Design Codes and Structural and Mechanical engineering textbooks often use the term to mean the fraction of total structural capability over that needed first sense.
If the margin is 1, it can withstand one additional load of equal force to the maximum load it was designed to support i.
There is a near universal push towards conservatism in the calculation of safety factors, i.