The real contact length during the grinding process is considered as an important subject for researchers, mainly because it reflects the intensity of the responses such as grinding forces and temperature generation. In order to measure and assess the real contact length, many experimental techniques and prediction models are available in the literature. Among all these models, the model developed by Rowe and Qi is being used widely by researchers because of its ability to make close predictions with real values. Rowe and Qi coined the term called roughness factor in their model. This factor varies with grinding environments and wheel-work material combinations. To decide it for a new environment, one has to do the laborious experimental work. In this article, the roughness factor has been analysed from the grinding temperature and the heat partition ratio point of view and expressed so that without experimental work prediction of the roughness factor can be done. For this, a new factor called as the thermal factor has been proposed based on the roughness factor modifications. Its good correlation with dimensionless temperature and heat partition ratio under different grinding environments have been presented and discussed in the current communication. It seems that the thermal factor can be helped in an easy and accurate prediction of the contact length during grinding operations. © 2014 Institution of Mechanical Engineers.