About CalcKit
CalcKit is a free collection of 280 online calculators for math, health, finance, and unit conversion. The project exists to make accurate, well-explained calculation tools available without paywalls, accounts, or data collection. Every calculation runs locally in your browser. Nothing you type — not your weight, your salary, or your loan details — is ever transmitted to a server. There is no sign-up flow and no usage tracking tied to your identity. What makes the collection different is the explanation that comes with each answer. Every calculator page documents the formula or method it uses, describes common real-world use cases, and answers the questions people actually ask about that calculation, from how amortization front-loads interest to why BMI misclassifies athletes. Browse the 64 finance tools like the Mortgage Calculator, or start from the homepage.