Universal Principles of Design, Revised and Updated

Factor of Safety

The use of more elements than is thought to be necessary to offset the effects of unknown variables and prevent system failure.1

Design requires dealing with unknowns. No matter how knowledgeable the designer and how thoroughly researched the design specification, basic assumptions about unknowns of one kind or another are inevitable in every design process. Factors of safety are used to offset the potential effects of these unknowns. This is achieved by adding materials and components to the system in order to make the design exceed the specification that is believed to be necessary to meet the design requirements. For example, designing an Internet service that can support one thousand users is straightforward. However, to ...