BIOCHLOR is a well-known simple tool for evaluating the transport of dissolved chlorinated solvents in ground-water, ideal for rapid screening and teaching. This work extends the BIOCHLOR model for the calculation of stable isotope ratios of carbon and chlorine isotopes in chioroethenes. An exact solution for the three-dimensional reactive transport of a chain of degrading compounds including sorption is provided in a spreadsheet and applied for modeling the transport of individual isotopes C-12,C-13, Cl-35, Cl-37 from a constant source. The model can consider secondary isotope effects that can occur in the breaking of C-Cl bonds. The model is correctly reproducing results for delta C-13 and delta Cl-37 modeled by a previously published 1-D numerical model without secondary isotope effects, and is also reproducing results from a microcosm experiment with secondary chlorine isotope effects. Two applications of the model using field data from literature are further given and discussed. The new BIOCHLOR-ISO model is distributed as a spreadsheet (MS EXCEL) along with this publication. (C) 2016 Elsevier B.V. All rights reserved.