Budgetron: The Simple Budget Planner
Starting initially as a personal project, Budgetron turned into a PWA ("Progressive Web App") that was developed to solve frustrations with regular calculators, as well as other budget applications. Designed with absolute simplicity in mind, Budgetron doesn't require any form of registration. It offers both a Web version demo - fully featured - and a Android application.
With an input starting point - either zero or a specific amount, the system allows you to keep precise track of where you are for a day's budget. Enter in the purchase's amount (without taxes), and it will subtract that from the original. With the ability to remove purchases from the list, it recalculates the amount as needed.
Budgetron can also handle tax calculation when called for! If you know the tax percentage of the area that you're in, it can be entered into the Settings and retained across uses. Unfortently, it currently is not possible to fetch it automatically due to the costs of doing so. Additionally, when you are working from a set amount, Budgetron can warn you when you're within a set percentage of your budget.