About us

CalcPrincipal (calcprincipal.com) is a free library of finance calculators: mortgages and home loans, personal and business borrowing, interest and savings, retirement and investing, debt payoff, rental property, and everyday money maths.

Who is behind it

The site is created and maintained by a small independent team — the CalcPrincipal team. Everything here is published under the site's name, never under a person's name. If a calculator produces a wrong figure, that is on the team, and the fix is too: the contact page is how you tell us.

How we work

Every calculator carries a "How this is calculated" note stating its formula and conventions: rates are nominal annual rates divided by their compounding periods unless labeled APY or AER; payments and contributions fall at period end; nothing is rounded until the displayed figure. Where a result depends on a model — the credit-card pages use a published daily-balance model — the model is printed beside the result. Acceptance figures for our formulas were verified against published references (open textbooks, regulator methodology) before the site was built.

What this site is not

Not financial advice. Calculators produce estimates from the figures you enter; they do not know your circumstances, and no page here offers, sells or recommends a financial product. For decisions about your money, a qualified, regulated professional who knows your situation is the right instrument.

Privacy by design

All calculations run in your browser. We do not ask for sign-up and we do not receive or store the numbers you type. Your currency preference is stored only in your own browser.