http://agrimetsoft.com/calculators/Mean%20Absolute%20Error.aspx
 
We have the result of a model and observation data in an excel file (or text file, or ...) and we want to calculate MAE (Mean Absolute Error) for this output of the model. You should prepare the data in two columns which the first column is observation data and the second one is model data. We should just copy the data from the file and paste it in "Online Calculator of MAE" then click on MAE button. 
Notice: you can type the data manually by space delimiter.