Finance calculators

Pure-math finance tools that don’t require an account, a newsletter signup, or your personal numbers leaving the browser. Tip, tax, and discount calculators ship first; mortgage, compound interest, and salary are next on the runway.

The mortgage calculator returns the monthly payment, total interest paid over the term, and the full amortization schedule from price, down payment, rate, and term — the four inputs that drive the number, with no required email capture. The compound-interest calculator handles arbitrary contribution frequencies (monthly, quarterly, annual) and any compounding period, which matters because the difference between annual and monthly compounding at 7% over 30 years is roughly 10% of the final balance. The salary calculator turns a gross figure into net annual, monthly, weekly, and hourly using the current US federal brackets, FICA, a configurable state rate, and pre-tax 401(k) — surfacing exactly which line item drives each marginal dollar so you can compare two offers in the right column. Tip, sales-tax, and discount calculators handle the everyday cases: split a bill, back-out a pre-tax price, or reverse-engineer the original price from a discount percentage. Every formula is the textbook one; nothing is sent to a server.