In this study, a total of 26 samples (17 from Zonguldak and 9 from Amasra) were collected. In order to correctly understand the effect of coal cleaning process on grindability, samples were cleaned at 1.60 g/cm(3) ZnCl2 solution and float samples were collected. Before and after this cleaning process, Hardgrove grindability indexes (HGI) of each coal samples (original and clean) were determined. Ash percentages show a decreasing trend by float and sink test for all samples studied as this was aimed and expected, while HGI showed an increase for Zonguldak coals and decrease for Amasra coals. However, total sulfur percentage decreases for Zonguldak coals and either increases or decreases for Amasra coals, and change in total sulfur has the most significant role in terms of HGI change. Taking abovementioned variations into consideration, new approaches were proposed to predict HGI after cleaning. Proposed methods of HGI after cleaning yielded a correlation coefficient of 0.88, 0.82, and 0.86 (R (2) = 0.88, R (2) = 0.82, and R (2) = 0.86) respectively for first, second, and third methods, which can be regarded as highly significant. With these approaches, one can easily understand the effect of cleaning process on grindability. In addition, easiness in coal grindability with correct understanding of parameter contribution would be achieved.