About DuckDollar

Hi. I'm Roland Sta. Romana, and I make every calculator on this site.

My degree is a BS in Mathematics, and I taught math before I taught myself to build websites. Those two jobs turned out to be the same job. In a classroom, the hard part was never getting a student to the right answer. The hard part was getting them to understand what the answer meant, and to believe it enough to act on it. A number nobody trusts is a number nobody uses.

Years later I was trying to work out how long it would take to clear a debt, and I ran into the same wall from the other side. The free calculators I found would give me a figure and nothing else. No formula. No assumptions. A few wanted my email before they would show the result at all. I was being asked to trust arithmetic I could not see, about my own money, by a site that would not tell me who wrote it.

Why the math is public

A calculator is a claim. If DuckDollar tells you your retirement number is $1.2 million, that is a serious thing to say to somebody, and you should be able to check it.

So every tool here publishes its formula, its assumptions, and its source. The inflation figures come from Bureau of Labor Statistics CPI data. The tax logic follows current IRS rules. The 4% withdrawal rate traces back to the 1998 Trinity Study, and the page says so, including where that study stops being reliable. You can read all of it on the methodology page, and the calculation engine itself is open source on GitHub.

If you find an error in any of it, tell me. I would rather be corrected than be wrong in public.

How the site stays free

There is no account, no trial, and no paywall on anything. I plan to run modest ads to cover hosting, and that will be the site's only source of income. I don't sell your data, because I never receive it: the math runs inside your browser tab, so the numbers you type never reach a server.

What this is not

I'm a mathematician and a builder, not a licensed financial advisor, and DuckDollar is education rather than advice. The formulas are accurate and documented. Your situation still has details no calculator knows about. Use these tools to think clearly, then talk to a professional before you act on a number.

Get in touch

Suggest a tool, report a bug, or argue with my math on the contact page. You can also find me on LinkedIn. I read everything.