Coast FIRE Calculator
Coast FIRE is the point where your current investments will grow into your retirement number on their own — no more contributions needed. Enter your age, retirement age, current savings, and target to find out if you're already coasting, and how much you'd need today if you're not. Works in any currency.
The portfolio you already have invested and growing.
Your FIRE target
At 4% your FIRE number is your annual spending × 25.
An example only — future returns aren't guaranteed.
If you're not coasting yet, we'll estimate when you could stop contributing.
Coast FIRE number today
in today's money
Coast FIRE assumes growth; a real return of 0% or more was used.
The withdrawal rate was adjusted into the 2–10% range.
Some values were above the allowed range and were capped for this calculation.
A real (after-inflation) return keeps your FIRE number in today's money.
Every calculation runs in your browser — nothing is sent to a server.
This is an arithmetic projection, not investment advice; market returns vary and aren't guaranteed.
The Moment You Stop Feeding the Portfolio
Coast FIRE marks a single, specific milestone: the point at which the money you've already invested is on track to grow, on its own, into the balance you'll need at retirement — even if you never deposit another dollar. Nothing about your job has to change. You can keep working full-time, switch to something you enjoy more, or take a lower-paying role, because the only thing you still need your income for is covering today's cost of living. Retirement itself is already funded by compounding that's already in motion.
That distinction matters because most FIRE planning treats "years to retirement" and "savings rate" as levers you pull together for decades straight. This calculator isolates one question instead: has time and growth already done enough of the work that you could stop contributing right now and still land on target? For a lot of people who started saving aggressively in their 20s and 30s, the honest answer arrives years before they expected it.
What Each Field Is Asking
- Current age and target retirement age set how many years compounding has left to run — this gap is the exponent in the formula below, so a few extra years makes a large difference.
- Current invested savings should be the balance actually sitting in the market (brokerage, index funds, retirement accounts) — cash reserves or home equity don't compound the way this projection assumes.
- Your FIRE target can be entered as an annual spending figure plus a withdrawal rate, or typed directly as a lump-sum number if you already know it from other planning.
- Expected real return should already be net of inflation — this keeps the FIRE number and the Coast FIRE number in the same, comparable units of today's money.
- Monthly contribution is optional and only used to answer a second question: if you're not coasting yet, roughly when would ongoing contributions get you there?
The Coast Number Is Just a Present Value
Coast FIRE number (today) = FIRE number ÷ (1 + real return) ^ years remaining
Projected balance (at retirement) = Current savings × (1 + real return) ^ years remaining
You're already coasting the moment your current savings meet or exceed the Coast FIRE number — which is mathematically identical to saying your projected balance at retirement meets or exceeds your FIRE number. The calculator also walks forward month by month with your contribution added: it finds the first month where your growing balance clears the (shrinking) present-value target for whatever years are left at that point, and reports that as your Coast FIRE age — the birthday you could stop contributing for good.
Three Worked Scenarios
Not coasting yet. Alex is 27, plans to retire at 65 (38 years out), spends $50,000/year at a 4% withdrawal rate (FIRE number $1,250,000), assumes a 6% real return, and has $80,000 invested. Coast number today: 1,250,000 ÷ 1.06^38 ≈ $136,550. Alex's $80,000 covers about 59% of that, leaving a gap of roughly $56,550 — the projected balance at 65 with zero further contributions would land near $732,340, about $517,660 short of the $1,250,000 target. Alex isn't coasting yet, but is closer than "38 years of saving left" makes it feel.
Already coasting. Priya is 42, retiring at 60 (18 years out), spends $40,000/year at 4% (FIRE number $1,000,000), assumes a 5% real return, and has $420,000 invested. Coast number today: 1,000,000 ÷ 1.05^18 ≈ $415,520. Priya's $420,000 clears it by about $4,480 — a thin but real surplus. Left untouched, that balance projects to roughly $1,010,780 at 60, about $10,780 above the FIRE number. Priya could stop contributing today and still arrive on schedule.
Finding the Coast FIRE age. Sam is 30, retiring at 65 (35 years out), has $50,000 invested, a $1,500,000 FIRE number, assumes a 7% real return, and keeps contributing $1,000/month. Today's coast number is about $140,490 — Sam's $50,000 is well short. But stepping forward month by month, the $1,000/month contributions push the balance past the shrinking present-value target around month 122, roughly age 40. From that point on — about a decade from now — Sam could stop contributing entirely and let growth finish the job alone.
How Much You Need Banked Today, by Years Left
Because the coast number is a present value, the share of your FIRE number you need already invested falls fast as your time horizon stretches out — and rises fast at higher assumed returns, since more of the work gets left to compounding.
| Years to retirement | 4% real return | 5% | 6% | 7% |
|---|---|---|---|---|
| 5 | 82% | 78% | 75% | 71% |
| 10 | 68% | 61% | 56% | 51% |
| 15 | 56% | 48% | 42% | 36% |
| 20 | 46% | 38% | 31% | 26% |
| 25 | 38% | 30% | 23% | 18% |
| 30 | 31% | 23% | 17% | 13% |
Where People Get Coast FIRE Wrong
- Reading "coasting" as "quit working." It only means the retirement portfolio no longer needs new contributions — your income still has to cover today's rent, food, and bills until the actual retirement date.
- Plugging in a nominal market return (often 9–10% for stocks) instead of a real one. That overstates growth by the inflation rate and makes the Coast FIRE number look artificially reachable.
- Treating the FIRE number as fixed for decades. A move, a new dependent, or a change in expected healthcare costs changes annual spending — and therefore both the FIRE number and the coast number — so it's worth rechecking after any major life change, not just once.
- Forgetting that this is a smooth average, not a market forecast. Real portfolios have down years; someone who reaches their coast number right before a downturn may dip below it again for a while, even though the long-run math still works out.
- Confusing this with Barista FIRE. Barista FIRE deliberately shrinks the target because ongoing part-time income offsets some retirement spending forever. Coast FIRE leaves the target exactly where it was — you've simply already banked enough for compounding alone to reach it.
What This Calculator Doesn't Do
It doesn't account for taxes on withdrawals or account type (taxable vs. tax-advantaged), sequence-of-returns risk from real market volatility, Social Security or pension income, or one-off expenses like a home purchase. Every figure — the coast number, the projected balance, and the Coast FIRE age — is a today's-money estimate built from a constant assumed return, not a forecast or investment advice. All of the math runs locally in your browser; nothing you type is uploaded or stored anywhere.
Sources & further reading
- U.S. SEC Investor.gov — official compound interest calculator and how growth compounds over time
- Consumer Financial Protection Bureau — retirement planning tools and withdrawal timing guidance
- U.S. Bureau of Labor Statistics — Consumer Price Index data behind real (after-inflation) return assumptions
- IRS Retirement Plans — contribution limits and account rules that shape how much you can keep investing
Frequently asked questions
What is Coast FIRE, and how is it different from full FIRE and Barista FIRE?
Coast FIRE is the moment your invested savings are already large enough that, with no further contributions, compound growth alone will carry them to your retirement number by your target age. With full FIRE you keep saving until your portfolio can fully fund retirement today; with Barista FIRE you cover some expenses with part-time income while your investments coast. This coast fire calculator shows the Coast FIRE number you'd need today, so you can see whether you can ease off aggressive saving and let compounding do the rest.
What is the Coast FIRE formula, with a worked example?
The core formula is: Coast number = FIRE number ÷ (1 + real return)^years to retirement. It's just the present value of your FIRE number. Example: if your FIRE number is 1,000,000, you're 35 with retirement at 65 (30 years), and you assume a 5% real return, then (1.05)^30 ≈ 4.32, so the Coast FIRE number today is about 231,400. If your current invested savings meet or beat that figure, this coast fire number calculator marks you as already coasting.
Why use a real (after-inflation) return instead of a nominal one?
Because it keeps every figure in today's money. If you discounted a future FIRE number using a nominal return, the answer would ignore inflation eating into your spending power. By using a real return — your expected return minus inflation, often assumed around 4–7% for a stock-heavy portfolio — the FIRE number and the Coast FIRE number both stay in today's dollars, so the coastfire calculator result is directly comparable to what you have now.
How does the 4% rule turn annual spending into a FIRE number?
The 4% rule (a rule of thumb from retirement research) says you can withdraw about 4% of your portfolio in the first year and adjust for inflation after. So your FIRE number = annual spending ÷ withdrawal rate — at 4% that's your annual spending × 25. Spending 40,000 a year implies a 1,000,000 FIRE number; a more cautious 3.5% rate implies about 1,143,000. This tool lets you enter spending with a withdrawal rate, or type a FIRE number directly.
Is this investment advice, and is anything sent to a server?
No. This is an arithmetic projection based on the numbers you type — it isn't investment advice, and real market returns vary and aren't guaranteed. Everything is computed in your browser; nothing is uploaded, there's no login, and your inputs never leave your device (they're only saved locally so the form remembers them). Use it to sanity-check whether you can stop saving for retirement, then confirm with a qualified advisor.