Pillar stability is an active research topic, and is important in the safety evaluation of underground mining projects. Commonly, pillar stability is evaluated using empirical formulations based on specific case studies and rock mass conditions. Numerical modelling could be a very useful tool given its ability to represent a wide range of field situations, as well as material behaviour. However, the evaluation of the safety factor using numerical models may be a challenging task when a large number of runs is required to yield a reliable estimate, e.g. strength reduction or load testing. In this context, a fast and accurate method of measuring pillar safety is desirable. The failure strain proposed by Sakurai (1981) was studied to understand and propose its use when adapted to room and pillar stability by means of numerical modelling. The commercial software package FLAC3D was used to evaluate the continuum mechanics problem. A wide range of parameters involved in the calculation were explored. Results suggest that the failure strain seems to be a promising tool when used correctly. Considerable time saving can be made without losing accuracy.