A small, fast, honest calculator for a question most tools bury behind a signup form.
beaverfi is a single-page Coast FIRE calculator, and it's free — not free-trial, not free-with-an-email. One page, no account, no upsell, and no step where you hand over an address to see your own numbers. Type, read the chart, close the tab.
It's the only tool here for now. More may follow, built the same way.
If those letters are new to you, they're worth ten seconds, because the whole calculator is built on them. They stack, so read them in order.
Financial independence is the point where your savings and investments can cover your living costs on their own, so working becomes something you choose rather than something you need. That's the fi in beaverfi.
It isn't a feeling or a lifestyle — it's a number. Roughly: enough invested that what it produces each year covers what you spend each year. A common rule of thumb puts that at about 25 times your annual spending, on the reasoning that you could withdraw about 4% of the balance a year and have it last. Spend $60,000 a year, and the target is around $1.5 million. That number is your FIRE number.
FIRE is financial independence pursued deliberately and ahead of the traditional schedule. Save an unusually high share of your income, invest it, and reach that number in your forties or fifties rather than your sixties.
The "retire early" half is optional, and plenty of people who reach FIRE keep working. What actually changes is that the paycheck stops being the thing holding everything up.
Here's the part most people haven't heard, and it's the useful one.
Money already invested keeps growing on its own. So there is a moment, well before you're financially independent, when you have enough invested that compound growth alone will carry you to your FIRE number by the age you picked — even if you never contribute another dollar.
That moment is Coast FIRE. You're not done, and you can't retire yet. But you're no longer required to save aggressively. From then on you only need to cover your current bills; retirement is already handled by money you set aside years ago.
A quick example. Suppose you're 30, you want $1.5 million by 60, and you assume 5% growth after inflation. Roughly $350,000 invested today would grow to about $1.5 million in those 30 years untouched. Cross $350,000 and you've hit Coast FIRE — you could stop contributing, take the lower-paying job you actually want, or drop to four days a week, and still land on target.
The calculator finds that crossing point for you, using your real balances, contributions, and assumptions, and shows you the year it happens.
Every assumption it makes — the three tax buckets, how the drawdown works, what it deliberately leaves out — is written up under "How this is modeled" at the bottom of the calculator, next to the numbers it applies to.
The calculator runs entirely in your browser as plain JavaScript. There is no server doing the math, so nothing you type is ever transmitted anywhere — not your salary, not your balances, not your retirement date.
The one exception is the "Support this tool" link, which is an ordinary link to Ko-fi. It loads nothing and knows nothing about you unless you choose to click it.
You don't have to take that on faith. Open your browser's developer tools, watch the Network tab, and fill in the whole calculator: you won't see a single outbound request. This site also sends a Content-Security-Policy that instructs your browser to refuse any script, style, font, or image from another domain — so it isn't only a promise, it's enforced on your end.
Because there's no account and no server, Save writes to the browser you're using, on the device you're using — that's the honest trade for not asking who you are. A scenario saved on your laptop won't appear on your phone, or even in a different browser on that same laptop. It can also vanish without warning if you clear site data, use private browsing, or a phone reclaims storage space.
So treat Save as a convenience, not a backup. To actually keep a scenario:
.json file you can back up anywhere; Import loads it on any device. This is the reliable one.
That's Chester. He runs the place.
Beavers are the right animal for this. They build steadily rather than quickly, they bank what they gather, and their dams hold because they keep patching them — which is more or less the entire thesis of financial independence, arrived at without a spreadsheet.
Chester's mentor is a software engineer based in California who is working toward FIRE himself. He built the calculator because he wanted an answer to a specific question — can I ease off now? — and every tool he found either oversimplified it, demanded an email address before showing a result, or quietly routed him to an affiliate link. So he wrote his own, put Chester on the door, and made it free.
There are no ads and no affiliate links here, and there won't be: a calculator meant to hand you an objective number shouldn't have a financial stake in the answer. If it saved you some time, a tip ☕ covers the hosting. That's the whole business model.
Questions, corrections, or a bug in the math? chester@beaverfi.com — Chester reads everything, and a corrected assumption is the most useful thing you can send.
beaverfi provides general educational information and arithmetic, not financial, tax, investment, or legal advice. It doesn't know your full situation and isn't a substitute for a professional who does. Projections are illustrations built on assumptions you choose; actual returns, inflation, tax law, and life will differ. Decisions you make with these numbers are your own.