LuniBound · Your private path to financial freedom
When could work become optional?
Everyone headed for financial independence has a landing date — the day work becomes optional. LuniBound charts your flight there: your FI number, the age you could land, your Coast FIRE point, and your odds across 500 simulated futures — and your moon fills in as you close the distance. It all runs in your browser: no account, no bank linking, and we can’t see your plan — by design.
Keep & share — files are created on your device
Estimates only — see the methodology and disclaimer below. Your inputs are stored only in this browser (local storage) so the page remembers them; they are never transmitted anywhere.
How it works — no black box
Read the full methodology — formulas, assumptions, limits and how we test the math →
The math
Your FI number is your yearly spending — minus any guaranteed retirement income — divided by your withdrawal rate (at 4%, that's 25× spending). We then grow what you have, plus your monthly contributions, month by month at your expected return until the portfolio reaches that number.
Monte Carlo
Real markets don't grow in a straight line. We simulate 500 futures where each year's return is drawn at random (lognormal) using your expected return and volatility — contributions are added at each year-end, a deliberate simplification. The percentage is how often the plan reached your FI number by age 65. Your expected return is treated as the average yearly return; because returns vary, the typical (median) future compounds a little more slowly than the expected path — so the median FI age is usually somewhat later than the expected one.
Your data
Every calculation happens in this page, on your device. There is no server version of your plan, no account, and no bank connection. Clear your browser data or hit Reset and it's gone — that's the point.
More calculators
Coast FIRE calculator
How much you need invested today so you can stop contributing.
Barista FIRE calculator
How part-time income shrinks the number you need.
Savings rate calculator
Years until you can retire at your savings rate.
How much do I need to retire?
Nest egg and monthly savings for your retirement age.
Questions
Is my financial data private?
Yes. Everything is calculated in your browser. Your inputs are saved only in this browser's local storage so you don't have to retype them — they are never sent to Lunibyte or anyone else. There is no account and no bank linking.
How is the FI number calculated?
Your FI number is your yearly spending in retirement divided by your safe withdrawal rate. At the classic 4% rate, that is 25 times yearly spending.
What does the Monte Carlo result mean?
We simulate 500 possible futures. Each year, investment returns are drawn at random from a distribution matching your expected return and volatility. The percentage shows in how many of those futures your portfolio reached your FI number by age 65, plus the median age it happened.
Are the returns inflation-adjusted?
Yes. Everything is shown in today's dollars: enter a real (after-inflation) expected return, commonly around 5–7% for a diversified stock portfolio.
What counts as guaranteed income?
Income you can count on every year once you stop working, without selling investments: a pension, rental income, an annuity, or Social Security if you'd retire at the age it starts. Every $1,000 a year of it lowers your FI number by $25,000 at a 4% withdrawal rate. Enter it in today's dollars, after tax if you can.
What is Coast FIRE?
Coast FIRE is the amount that, if you stopped contributing today, would grow on its own to your full FI number by your target age. Once you pass it, you only need to earn enough to cover current spending.
Is this financial advice?
No. LuniBound is an educational calculator. Results are estimates based on the numbers and assumptions you enter and are not financial, tax, or investment advice.
LuniBound Pro is coming
Planned: save multiple plans on your device, compare scenarios side by side, historical stress-testing back to 1872, and a printable one-page PDF report — still with no account and no data leaving your machine.
One email when Pro launches. Nothing else.