We present HNC-Plot, an Excel Visual Basic Application (Excel VBA) that can easily be used to create graphical plots of fluids associated with volcanic gases or geothermal manifestations, based on their helium, nitrogen and CO2 isotope data. HNC-Plot has been designed in a simple way; all the user has to do is to input data in an Excel spreadsheet. The spreadsheet also contains buttons which have links to Excel VBA codes that generate plots. Once, the respective button is clicked, and all required variables are defined, Excel VBA generates a plot with labels and axes. Based upon the user preferences, additional tasks such as construction of mixing lines between mantle and crustal gases or calculation of end-member proportions can also be performed. We sincerely believe geoscientists can quickly and easily create these plots, free of charge, with this application. This study also presents previously published data from related literature to show the foundations of the application and to present sample plots created with it.