LuniBound · Free calculator
Coast FIRE calculator
How much do you need invested today so that, without adding another dollar, it grows into your full FI number by the time you retire? Enter your numbers — everything is calculated on your device.
Estimates in today's dollars — see the assumptions below. Your inputs stay in this browser and are never transmitted.
What is Coast FIRE?
Coast FIRE is the point where the money you have already invested is enough to grow into your full retirement number on its own. You haven't retired yet — you still need to earn enough to pay today's bills — but you no longer have to save for retirement. Every contribution after that point is optional, which is why many people use Coast FIRE as a milestone for switching to lower-stress work, going part-time, or taking a career break.
Full FIRE (financial independence, retire early) means your portfolio can already pay for your life. Coast FIRE is the halfway house: your future is funded, your present still runs on a paycheck.
How the Coast FIRE number is calculated
Coast number = FI number ÷ (1 + real return)years until retirement
The first line turns your retirement spending into a target portfolio: at a 4% withdrawal rate, that's 25 times a year of spending. The second line works backwards: how much would you need today so that compound growth alone reaches that target by your retirement age?
Worked example
You're 35, want to retire at 65, and expect to spend $48,000 a year. At a 4% withdrawal rate your FI number is $1,200,000. With a 7% real return over 30 years, money grows about 7.6-fold (1.0730), so your Coast number today is about $157,641. With $50,000 invested and $1,000 added each month, you'd cross that line at around age 40.8 — and from then on, the rest is optional.
Use real returns, and test a cautious one
This calculator works in today's dollars, so enter a real return — what you expect after inflation. Diversified stock portfolios have historically returned roughly 5–7% a year after inflation, but there is no guarantee, and decades of below-average returns do happen. Because the Coast number depends heavily on the return you assume, it's worth checking how it changes at 5% as well as 7%. The longer your horizon, the more sensitive it is.
What this calculator leaves out
- Market swings. It assumes a steady average return. To see the range of outcomes across 500 simulated market paths, use the full LuniBound planner.
- Taxes and fees. Not modeled — lower your return to account for fund fees, and remember withdrawals from pre-tax accounts are taxed.
- Other income in retirement. Social Security or a pension would reduce the portfolio you need; they're not included here.
See your whole plan on one page
The LuniBound planner adds 500 simulated market futures, a growth chart, Coast FIRE and your moon progress — still 100% in your browser, with no account and no bank linking.
Open the full plannerQuestions
What is a good Coast FIRE number?
There's no universal figure — it depends on how much you'll spend in retirement and how many years your money has to grow. Someone 30 years from retirement needs far less invested today than someone 10 years away, because compounding does more of the work.
Should I enter a nominal or real return?
Enter a real return (after inflation). All amounts on this page are in today's dollars, so a real return keeps everything consistent without a separate inflation setting.
What happens after I reach Coast FIRE?
Your retirement is projected to be funded if your investments earn the return you assumed, so you only need income to cover current living costs. Many people keep contributing anyway as a safety margin against weaker returns.
Is Coast FIRE the same as Barista FIRE?
No. Coast FIRE means you stop saving but keep earning enough to live on until a normal retirement age. Barista FIRE means you start drawing on your portfolio early while part-time income covers the rest of your spending.
Is my data private?
Yes. Everything is calculated in your browser and saved only in this browser's local storage so you don't have to retype it. Nothing you enter is sent to Lunibyte or anyone else.