Coast FIRE Calculator — Can I Stop Contributing?
Enter your current age, retirement savings, monthly contributions, and planned retirement spending. The calculator finds the exact age you can stop contributing and let compound interest carry you to financial independence.
What is Coast FIRE?
You are burned out. You have $280,000 saved at 38. A friend mentions “Coast FIRE” and suddenly there might be a way out of the grind — one that does not require another 25 years of maxing every account and eating ramen on principle.
Coast FIRE is the point at which your current retirement savings — with zero additional contributions — will compound to your Financial Independence (FI) number by your target retirement age, assuming a historical market return. You have done the heavy lifting. Now you let the market do it for you.
This is different from traditional FIRE (Financial Independence, Retire Early), where you accumulate enough to retire and live entirely off withdrawals right now. It is also different from Lean FIRE (retiring on a minimal budget) or Fat FIRE (retiring on a generous one) — those are spending variants. Coast FIRE is about when you can stop contributing, not when you can stop working.
The practical implication is enormous. Once you hit your Coast FIRE number, your job just needs to cover current living expenses — not retirement savings too. That $90,000 stressful job you hate becomes optional. The $45,000 part-time job you love becomes viable. The math still works.
The Coast FIRE formula explained
Coast FIRE builds on two well-established retirement planning concepts: the 4% safe withdrawal rate and the future value of money formula.
Annual spending is what you plan to spend each year in retirement. 25× comes from the 4% safe withdrawal rate — withdrawing 4% of a portfolio annually has historically sustained 30+ year retirements in the vast majority of market scenarios. r is your expected annual return (7% is the widely cited long-run real return of a broad US stock market index after inflation). years is the number of years between today and your planned retirement age.
Example: A 38-year-old planning to retire at 65 expecting to spend $4,000 per month ($48,000 per year) calculates as follows:
If this person has $213,000 saved today and invests it in a broad index fund, it will grow to approximately $1,200,000 by age 65 — without a single additional contribution.
The burnout math — why Coast FIRE changes everything
The r/personalfinance and r/financialindependence communities light up every time someone posts: “I calculated my Coast FIRE number and I have already hit it.” The responses are reliably ecstatic — and for good reason. The psychological weight of “I must maximize every account forever or I will be poor at 80” suddenly lifts.
When you hit Coast FIRE, the math only requires your income to cover your current bills. Nothing needs to go toward retirement anymore. This is the moment when lifestyle decisions become legitimate financial choices rather than irresponsible ones. Take the $30,000 per year nonprofit job you have always wanted. Reduce to part-time. Move to a lower cost-of-living city. Start the side business with the lower guaranteed income.
Barista FIRE is this concept under a different name — named after taking a coffee shop job for its flexible hours and health benefits while your portfolio compounds untouched. The financial mechanics are identical to Coast FIRE; the only difference is framing. Both mean: you have saved enough for compound interest to handle retirement, and your job now just needs to pay today’s bills.
The emotional permission to step off the treadmill when the math permits is one of the most underrated aspects of personal finance. Coast FIRE makes that permission legible and calculable — not just a vague feeling that you are “doing okay.”
Coast FIRE vs Traditional FIRE — key differences
The two strategies serve different goals. Understanding where each fits helps you decide which number to optimise for.
| Factor | Coast FIRE | Traditional FIRE |
|---|---|---|
| Retirement date | Your target age — you still work until then | Now (or as soon as the number is hit) |
| Contributions required | Zero — once Coast number is hit | Until full FI number is accumulated |
| Career flexibility | High — any job covering bills works | Full optionality — work is entirely optional |
| Portfolio size needed | Much smaller — time does the compounding | Full 25× annual spending at time of retirement |
| Risk level | Sequence risk deferred; decades of growth ahead | Sequence of returns risk highest at retirement |
| Best for | Burned-out accumulators with 15–30 years to retirement | People ready to retire now or within a few years |
How market returns affect your Coast FIRE number
The assumed annual return is the single most sensitive variable in the Coast FIRE formula. Because returns compound over decades, small differences in rate produce large differences in the Coast FIRE number. A 38-year-old targeting a $1,200,000 FI number (27 years to retirement) faces this range depending on their return assumption:
| Annual return | Coast FIRE Number (27 yrs to retire) | Difference vs 7% baseline |
|---|---|---|
| 5% | $325,000 | +$141,000 more needed |
| 6% | $252,000 | +$68,000 more needed |
| 7% | $184,000 | Baseline |
| 8% | $136,000 | $48,000 less needed |
| 9% | $101,000 | $83,000 less needed |
Based on a $1,200,000 FI Number ($48,000/year spending) with 27 years to retirement. Using 9% instead of 5% reduces the Coast number by $224,000 — a massive difference. Financial planners generally recommend 5–7% for conservative planning; 7% is often cited as the historical real return of a broad US index after inflation.
This is why it is important to plan conservatively. If you use 9% and the market delivers 5%, you will arrive at retirement short of your FI number. The calculator defaults to 7% as a middle-ground, historically grounded estimate — but you should stress-test your own plan at 5% and 6% to ensure you have margin.
The biggest risks of coasting too early
Coast FIRE is genuinely powerful — but it is not risk-free. Five scenarios can break the math after you stop contributing:
Lifestyle inflation erodes the FI Number assumption
Your Coast FIRE number is calculated against a specific annual spending target. If your lifestyle expands — bigger house, kids, private school, elder care — your FI Number rises and your Coast number becomes insufficient. Recalculate whenever your spending assumptions change materially.
Sequence of returns risk in the coasting years
If a severe market downturn (say, 2008–2009 or worse) happens in the decade after you stop contributing, your portfolio may fall below the level needed to recover to your FI Number by retirement. You have no new contributions to buy the dip. Running Monte Carlo simulations or stress-testing against historical worst-case sequences gives a more honest picture than a single-rate projection.
Career re-entry risk
Stepping back to a lower-paying or lower-stress role is easy. Getting back into a high-earning career after years away can be genuinely difficult — especially in fields that value continuous experience (law, medicine, engineering, finance). If the market underperforms and you need to resume heavy contributions at age 50, that option may be more limited than it looks at 40.
Health insurance gap (ages 45–64)
For Americans, the period between leaving a benefits-providing job and Medicare eligibility at 65 is the most expensive insurance window of your life. ACA marketplace plans for a 55-year-old couple can exceed $1,500–$2,500 per month in premiums alone, depending on income and location. Build this into your “bills covered by work” assumption — it is often the budget item that makes coasting on a lower income infeasible.
Life events reset the math
Divorce legally splits assets. A child with significant medical needs changes the spending trajectory permanently. A serious illness can decimate both income and savings simultaneously. Coast FIRE is a plan built on a set of assumptions — modeling your most probable path is reasonable, but maintaining a buffer above the minimum Coast number is prudent.
Related calculators
Coast FIRE fits within a broader financial independence toolkit. Once you know your Coast number, these calculators help you model what comes next.
FIRE Calculator
Calculate your full FIRE number and years to traditional financial independence
Retirement Planner
Year-by-year retirement gap analysis with projected balance vs target
Wealth Growth Calculator
See exactly how compound interest builds wealth over any time horizon
Compound Interest Calculator
Visualise compound growth on a lump sum with or without monthly additions
Roth IRA Calculator
Project tax-free Roth IRA growth — ideal for Coast FIRE savers under 50
4% Rule Calculator
Model safe withdrawal scenarios and portfolio longevity in retirement
Official resources and further reading
DOL — Savings Fitness: A Guide to Your Money and Your Financial Future
The U.S. Department of Labor's official guide to retirement savings — includes the 4% rule framework, asset allocation by age, Social Security integration, and step-by-step worksheets for calculating your retirement target. The foundational source for the 25× spending rule used in Coast FIRE calculations.
SSA — Retirement Benefits: When to Start Receiving
The Social Security Administration's official benefit estimator. Coast FIRE planners often undercount Social Security — even a $1,200/month benefit at 67 reduces the FI Number by $360,000 (using the 4% rule). Check your own projected benefit before finalising your Coast number.
Bengen (1994) — "Determining Withdrawal Rates Using Historical Data" — Journal of Financial Planning
The original 1994 academic paper by William Bengen that established the 4% safe withdrawal rate — the foundation of every FI Number calculation. Bengen tested withdrawal rates against 50 years of historical market data across multiple 30-year retirement windows. This is the primary source for the 25× rule.
Frequently asked questions
What is the difference between Coast FIRE and Barista FIRE?
They describe the same financial position from different angles. Coast FIRE is the mathematical threshold — the point where your savings will compound to your FI Number by retirement without additional contributions. Barista FIRE is the lifestyle strategy of responding to that threshold by taking a lower-stress job (stereotypically a coffee shop) that covers current expenses while the portfolio coasts. Barista FIRE practitioners have typically hit their Coast FIRE number.
Is 7% a realistic return assumption for Coast FIRE calculations?
The 7% figure refers to the inflation-adjusted (real) long-run average annual return of the broad US stock market, most often referenced as the historical S&P 500 average minus ~3% inflation. It is a reasonable central estimate for a diversified equity portfolio held over 20+ years. For conservative planning, use 5–6%. For aggressive or internationally diversified portfolios, 7–8% is common. Never rely on a single scenario — run your numbers at 5% and 7% and check whether both outcomes are acceptable.
Can I use Coast FIRE with a Roth IRA and 401k combined?
Yes. The Coast FIRE formula does not distinguish between account types — it operates on total investable assets. A Roth IRA and a 401k both compound tax-advantaged until withdrawal, so their combined balance feeds into your Coast FIRE number directly. The main consideration is whether your Coast strategy involves a job gap before age 59½ that would require penalty-free access to funds — in that case, Roth contribution basis (not earnings) can be withdrawn penalty-free, which matters for the years between coasting and traditional retirement age.
What happens if I hit Coast FIRE but the market crashes right after?
This is sequence-of-returns risk. If a significant market decline (e.g., 40–50%) happens shortly after you stop contributing, your portfolio may fall below the level required to recover to your FI Number by retirement. Because you are no longer contributing, you cannot buy the dip to accelerate recovery. The best protection is building a buffer — hitting 110–125% of your minimum Coast FIRE number before stopping contributions. If the crash happens and you are significantly below target, resuming moderate contributions during the recovery years dramatically improves outcomes.
At what age is it too late to benefit from Coast FIRE?
Coast FIRE depends on the number of compounding years between today and retirement. With fewer than 10 years to a target retirement age at 65, the Coast FIRE number approaches the full FI number itself — there is not enough time for compounding to close the gap. The concept is most powerful for people aged 30–50 with 15+ years of runway. That said, even at 55 with a retirement target of 70, the 15-year window reduces a $1.2M FI Number to a Coast target of about $444,000 at 7% — still meaningfully below the full target for many savers.
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