Thermodynamics has been fundamental to the interpretation of geologic data and modeling of geologic systems for decades. However, more recent advancements in computational capabilities and a marked increase in researchers' accessibility to computing tools has outpaced the functionality and extensibility of currently available modeling tools. Here, we present VESIcal (Volatile Equilibria and Saturation Identification calculator): the first comprehensive modeling tool for H2O, CO2, and mixed (H2O‐CO2) solubility in silicate melts that: (a) allows users access to seven of the most popular models, plus easy inter‐comparison between models; (b) provides universal functionality for all models (e.g., functions for calculating saturation pressures, degassing paths, etc.); (c) can process large datasets (1,000s of samples) automatically; (d) can output computed data into an Excel spreadsheet or CSV file for simple post‐modeling analysis; (e) integrates plotting capabilities directly within the tool; and (f) provides all of these within the framework of a python library, making the tool extensible by the user and allowing any of the model functions to be incorporated into any other code capable of calling python. The tool is presented within this manuscript, which may be read as a static PDF but is better experienced via the Jupyter Notebook version of this manuscript. Here, we present worked examples accessible to python users with a range of skill levels. The basic functions of VESIcal can also be accessed via a web app (https://vesical.anvil.app). The VESIcal python library is open‐source and available for download at https://github.com/kaylai/VESIcal, or it can be installed using pip. It is recommended to read and interact with this manuscript as an executable Jupyter Notebook, available at https://mybinder.org/v2/gh/kaylai/vesical-binder/HEAD?filepath=Manuscript.ipynb. Plain Language Summary: Geologists use numerical models to understand and predict how volcanoes behave during storage (preeruption), eruption, and the composition and amount of volcanic gas released into the atmosphere of Earth and other planets. Most models are made by performing experiments on a limited data set and creating a model that applies to that data set. Some models combine lots of these individual models to make a generalized model that can apply to lots of different volcanoes. Many of these different models exist, and they all have specific uses, limitations, and pitfalls. Here, we present the first tool, VESIcal, which acts as a simple interface to seven of the most commonly used models. VESIcal is written in python, so users can use VESIcal as an application or include it in their own models. VESIcal is the first tool that allows geologists to model thousands of data points automatically and provides a simple platform to compare results from different models in a way never before possible. Key Points: The first comprehensive volatile solubility tool capable of processing large datasets automaticallySeven built‐in solubility models, with automatic calculation and plotting functionalityBuilt in python and easily usable by scientists with any level of coding skill [ABSTRACT FROM AUTHOR]