How to Build a Personal Finance Calculator with Vanilla JavaScript

How to Build a Personal Finance Calculator with Vanilla JavaScript No frameworks. No build tools. Just HTML, CSS, and JavaScript — and a working finance calculator you can ship today. This tutorial walks through building a compound interest calculator from scratch, the same way the 155+ finance calculators at Profiterole were built — real web tools without any framework overhead. Why Vanilla JS for Finance Apps? Finance calculators are a great fit for vanilla JS: No loading overhead — users want instant results, not a React hydration delay No dependencies to maintain — a calculator written today still works in 5 years Trivially hostable — GitHub Pages, any static host, zero cost Easy to audit — financial logic in plain JS is readable by anyone The Formula Compound interest: A = P(1 + r/n)^(nt) Where A = final amount, P = principal, r = annual rate (decimal), n = compounds/year, t = years. Step 1: The HTML Form <label> Principal ($) <input type= "number" id= "principal" value= "10000" >