About Compound Snowball

Why this exists

I built Compound Snowball out of a specific frustration: most compound interest calculators give you a single number and stop there. No sense of how much of that number is your own money versus interest actually earned, no easy way to see what happens if you contribute a bit more each month, and no way to line up a couple of "what if" scenarios side by side to see which one actually gets you where you want to go. So I built the calculator I wanted to use myself, then kept adding to it (a debt payoff planner, a savings goal calculator, a dividend reinvestment calculator) whenever the same "I wish this existed" feeling came up again.

What it does (and doesn't do)

Every calculator here runs an animated chart that breaks your balance into contributions versus growth, so you can see at a glance how much of the result is money you put in versus money the math added on top. Where it's relevant, there's an inflation-adjustment toggle and a scenario comparison chart for testing a few different assumptions against each other, side by side, instead of re-running the numbers in your head.

What it doesn't do is give you financial advice. Every number on this site is an estimate based on the assumptions you type in: a rate of return, a timeline, a monthly contribution. And real markets, real interest rates, and real life don't follow a straight line. Treat the output as a way to build intuition and compare options, not a guarantee or a recommendation. For anything that actually matters to your finances, a licensed financial advisor who knows your full situation is worth more than any calculator, including this one.

How it's built, and how it makes money

There's no account to create and no data sent to a server: every calculation runs directly in your browser using plain JavaScript, and the only thing saved locally is whatever you choose to leave in your own browser's storage, like your last-used numbers, so you don't have to retype them every time you come back. I don't see your numbers, and I couldn't sell them even if I wanted to.

The site is supported by ads, which is the honest, unglamorous answer to "how does a free tool like this stay online." It's also why I'd rather build something genuinely useful than something that just looks impressive: a calculator people actually bookmark and come back to is worth more, to both of us, than one that gets used once and forgotten.

Found a bug, or want something added?

This is a small, independently run site, which means issues get fixed by one person reading their email rather than a support queue. If a number looks wrong, a page breaks, or there's a calculator you wish existed, get in touch. I read everything and I'd genuinely like to know.