Yanfly Engine Plugins is a plugin library made for RPG Maker MV, a wonderful piece of software to help you make that role playing game of your dreams. You can find out more about RPG Maker MV here.
You can access the tool here.
For those using the Class Base Parameters plugin, developers are given the option to create their own EXP formula. This tool exists to help game developers figure out what kind of formula to use for their game.