Explain it like I’m 5
Planting a tree is hard work at first: you dig, water and care for it. But once it’s big enough, it keeps growing on its own — you don’t have to do anything.
Retirement savings work the same way. Coast FIRE means you’ve already planted enough that, even if you never save another dollar, your money will grow into everything you need for retirement by itself. After that, you only need to earn enough to pay today’s bills.
This calculator tells you how big your “tree” needs to be today, whether you’re there yet, and — if not — how long it’ll take with the savings you add each month.
Words you’ll see, in plain English
- FIRE
- “Financial Independence, Retire Early” — saving and investing enough that your investments pay for your life, so work becomes optional.
- Coast FIRE
- Having saved enough that, even if you never save another dollar, your money will grow into your full retirement amount by itself.
- Withdrawal rate / 4% rule
- How much of your savings you take out each year in retirement. The “4% rule” says taking 4% a year has historically lasted about 30 years.
- Real return
- How much your money grows after you take away inflation. If your money grows 7% but prices grow 3%, you are really about 4% richer.
- Inflation
- Prices slowly going up over time, so the same dollar buys a little less each year. A candy bar that cost $1 might cost $1.03 next year.
- Compound interest
- Interest that earns its own interest. Like a snowball rolling downhill: the bigger it gets, the faster it grows.
More money words explained simply in our glossary.
What Coast FIRE means
FIRE stands for Financial Independence, Retire Early. Reaching full FIRE means your investments can cover your spending forever. Coast FIRE is an earlier milestone: you have saved enough that, even if you never invest another dollar, your portfolio should grow to your full FIRE number by the time you want to retire. From that point on you only need to earn enough to pay your current bills — which can mean less stressful work, part-time work, or simply more freedom.
How the Coast FIRE number is calculated
FIRE number = annual retirement spending ÷ withdrawal rate
Coast FIRE number = FIRE number ÷ (1 + real return)years to retirement
Real return = (1 + investment return) ÷ (1 + inflation) − 1
Because the calculator uses a real (inflation-adjusted) return, every figure is in today’s dollars. Your spending target, FIRE number and Coast FIRE number can be compared directly with what you have now.
Worked example
Say you want to spend $50,000 a year in retirement and use a 4% withdrawal rate. Your FIRE number is $50,000 ÷ 0.04 = $1,250,000. With a 7% return and 3% inflation, your real return is about 3.88%. If you’re 32 and want to retire at 60, that’s 28 years of growth, so your Coast FIRE number is $1,250,000 ÷ 1.038828 ≈ $430,000. If you have $100,000 invested today, you are not there yet — but investing $2,000 a month would get you there at about age 52, after which you could stop contributing entirely and still be on track to retire at 60. The chart above shows the same scenario.
How to read the chart
- Required balance (dashed) — how much you need at each age to coast to your FIRE number. It rises over time because you have fewer years left to compound.
- Keep contributing, then coast — your balance if you keep investing your monthly amount until you reach Coast FIRE, then stop. Where it meets the dashed line is your Coast FIRE age.
- If you stop saving today — your current balance growing on its own. If it starts below the dashed line, it stays below: without new money, you are always the same distance (in percentage terms) from coasting.
The calculator treats your monthly contribution as fixed in today’s dollars, so it effectively rises with inflation.
Things that can move your Coast FIRE date
- Sequence of returns: markets don’t grow evenly. A bad decade early on can delay coasting even if long-run averages hold.
- Fees: a 1% advisory or fund fee lowers your real return by about 1 point — a big difference over decades.
- Spending creep: a higher retirement budget raises both your FIRE number and your Coast number.
- Other income: Social Security, pensions or rental income reduce the spending your portfolio must cover.
Frequently asked questions
What is Coast FIRE?
Coast FIRE means you have already invested enough that, with no further contributions, compound growth alone should take your portfolio to your full retirement number by your target retirement age. You still need to earn enough to cover your living expenses until then, but you no longer need to save for retirement.
What is my Coast FIRE number?
Your Coast FIRE number is your full FIRE number discounted back to today: FIRE number ÷ (1 + real return)^(years until retirement). Your FIRE number is your annual retirement spending divided by your withdrawal rate — for example, $40,000 ÷ 4% = $1,000,000.
What return should I use?
Many FIRE planners use a nominal stock return of 6–8% with 2–3% inflation, which works out to a real return of roughly 4–5%. Using a lower return is more conservative. The calculator converts your nominal return and inflation into a real return, so all results are in today’s dollars.
Is the 4% rule still safe?
The 4% rule comes from studies of historical US market returns (Bengen 1994 and the later Trinity study), which found that withdrawing 4% of the starting portfolio, adjusted for inflation, survived most 30-year periods. For retirements longer than 30 years, or to be more cautious, many people use 3–3.5%.
What is the difference between Coast FIRE, Lean FIRE and Barista FIRE?
Coast FIRE: enough invested to stop saving, but you still work to cover expenses. Barista FIRE: you quit your main career and use part-time income to cover part of your spending while the portfolio covers the rest. Lean FIRE: full retirement on a minimal budget. Fat FIRE: full retirement with a generous budget.
Should I include my home equity or Social Security?
Only include invested assets you plan to draw from, such as brokerage, 401(k) and IRA balances. Leave out home equity unless you plan to sell. If you expect Social Security or a pension, reduce your annual spending by that expected income to get a smaller, more realistic FIRE number.
These results are estimates for education only, based on the assumptions you enter. They are not financial, investment or tax advice. Real returns, rates and taxes vary. See our methodology anddisclaimer.