Vinicius Fonseca

Hi, I'm Vinicius. I'm not an economist or a financial advisor — just an ordinary person who likes to understand his own numbers.

Why I built this site

It started from a personal wish: to always have a practical tool at hand, with the math open and a quick answer, for the money decisions in my own day — from comparing an investment to simulating a loan. Since I'm not an expert, I wanted something I could understand and double-check myself. Then I realized that what helped me could help others in the same situation: people who need a fast, reliable answer without a complicated spreadsheet or a sign-up. I opened the site for them — and for me.

I do it honestly: the numbers are checked against official sources (you can see the process in How we calculate), but they remain planning estimates, not investment advice. The final decision is always yours.

Get in touch

Found an error, have a suggestion, or want a new calculator? Email contact@calculatorsmoney.com or find me on LinkedIn.

How every calculator is checked

Writing a formula and trusting it is not enough. Every calculation published here goes through three checks before it goes live, and that is what lets me stand behind a number without being an economist:

The formula is re-implemented from scratch, from the underlying financial mathematics, by a different route from the code that runs on the page. If the two results disagree to the cent, the calculator does not ship. Checking code against itself proves nothing, so the second calculation never starts from the first.
Every number that appears in the text comes out of the calculator itself, never typed by hand. A worked example is a measured example: if a page says that 200 a month at 0.6% for ten years becomes a given amount, that figure came off the tool on screen.
Rates, brackets and indices carry an explicit reference year, in the code and on the page. When a rate or a rule changes, the update is made by reading the official source — a central bank, a tax authority, a regulator — not by copying another website.

Where the numbers come from

None of the maths here is invented: compound interest, level-payment and constant-principal amortisation schedules, present and future value, internal rate of return, the Rule of 72 and the 4% rule (Bengen, 1994) are standard finance, and you can reproduce any of them in a spreadsheet. For figures that change over time the references are the U.S. Federal Reserve, the IRS, the SEC and the OECD. How we calculate sets out each one.

What this site is not

None of this is investment advice or financial consulting. No calculator here knows your income, your debts, your job security or how you would sleep after a 30% drawdown, and nothing on this site should be read as a recommendation to buy, sell or hold anything. The output is arithmetic on the assumptions you type in — change an assumption and the answer changes with it.

There is a second limit worth stating plainly, because this site is read in six languages. Interest conventions, taxes and retirement rules differ from country to country, and they change over time. The same compound interest result is identical everywhere as pure maths; what it is worth after tax in your country is not. Withholding on gains, inflation indices, deductible contributions, how a loan's effective rate must be disclosed — all of that is local law. Take any number from here to an official source in your own jurisdiction, or to a professional who works under it, before you act on it.

I also never see what you type: the maths runs inside your browser, and the values you enter are not sent to any server and are not stored by me.

Found an error? Tell me

A wrong result is the kind of problem I want to hear about the same day. Write to contact@calculatorsmoney.com or use the contact page with three things: which calculator, which values you entered, and what result you expected. With those three I can reproduce the case and correct it. A fix always jumps the queue ahead of a new feature.