Purpose - The purpose of this paper is to give a comprehensive description of various safety factors that need to be determined while assessing the short-circuit strength of transformers. Design/methodology/approach - Factors of safety are divided into two categories: radial and axial. Some of the latest approaches in assessing the strength are elaborated. Findings - Six major sets of calculations are identified: three each for radial and axial electromagnetic forces. Corresponding factors of safety are defined and calculated for practical transformers. These factors are related to the strength and stability aspects of windings. Research limitations/implications - The work gives pointers for further research at appropriate places while highlighting the challenges involved in the assessment of the short-circuit strength. Practical implications - The presented overview of the factors of safety can be a useful guide for the practicing transformer engineers. Originality/value - The main contribution of the reported work is in highlighting the intricacies associated with the subject of short-circuit strength of power transformers. It can serve as a reference document for future research works in the area since the procedures are outlined for calculating the factors of safety through six case studies. © 2012 Emerald Group Publishing Limited. All rights reserved.