A Microsoft Visital Basic program, WinCcac, has been developed to calculate the structural formulae of chlorite. WinCcac classifies rock-forming chlorite group minerals based on 14 oxygens for complete chlorite analyses. For electron-microprobe-derived chlorite analyses site occupancy can be estimated by using the stoichiometric H2O (wt%) and Fe2O3 (wt%) contents. The program is created to predict cation site-allocations at the different structural positions such as the tetrahedral, octahedral, and interlayer sites. Furthermore, various chlorite geothermometers based on an empirical approach are carried out to specify the condition of formation temperature. WinCcac allows the user to enter and load multiple chlorite analyses in its own data entry window, to edit and load Microsoft Excel files in estimating and classifying chlorite data, and to generate and store all the calculated results in the output of Microsoft Excel file for further data evaluation and graphing purposes. (C) 2015 Elsevier Ltd. All rights reserved.