A simple model for the Arrhenius reaction conodont Color Alteration Index (CAI) that can be implemented easily in a computer program is introduced. The model, named to as EasyCAI, envisages the overall process of conodont alteration as a series of 12 parallel pseudo-first-order reactions. Our approach is especially amenable to a spreadsheet program and can solve complex geological histories involving variable heating and cooling rates. With EasyCAI, a profile of CAI values versus time can be obtained for a given stratigraphic level if the time-temperature history for that level has been estimated. EasyCAI can provide additional constraints to optimize thermal history models by computing profiles of CAI values with depth and time; thus providing a new tool for quantitative CAI palaeothermometric analysis. (C) 2010 Elsevier B.V. All rights reserved.