CoastFIRE is the variant of FIRE that asks a different question. Traditional FIRE asks: "How fast can I accumulate 25x my expenses?" CoastFIRE asks: "How much do I need to save before I can stop saving and let compound growth do the rest?"
The answer is usually less than you think — and much less than full FIRE — because time and compounding are doing the heavy lifting. The trade-off: you don't retire early. You continue working, but you work on your terms — lower stress, lower pay, more meaning — because every dollar you earn goes to current expenses, not to building a retirement portfolio.
The CoastFIRE number depends on three variables:
Formula: CoastFIRE Number = Target Portfolio / (1 + real return)^years
Assuming a target of $1,500,000 at age 65 (supporting ~$60,000/year at 4%):
| Current Age | Years to 65 | CoastFIRE Number (5% real) | CoastFIRE Number (7% real) |
|---|---|---|---|
| 25 | 40 | $213,000 | $100,000 |
| 28 | 37 | $246,000 | $122,000 |
| 30 | 35 | $271,000 | $140,000 |
| 33 | 32 | $314,000 | $172,000 |
| 35 | 30 | $347,000 | $197,000 |
| 38 | 27 | $402,000 | $242,000 |
| 40 | 25 | $443,000 | $277,000 |
| 45 | 20 | $565,000 | $388,000 |
| 50 | 15 | $721,000 | $543,000 |
A 30-year-old who has saved $271,000 in retirement accounts can — mathematically — stop saving entirely. If they continue working to cover current expenses and the market returns an average 5% real, they'll have $1.5M at 65.
At a 7% real return (closer to US equity historical average), the numbers are even more forgiving. A 25-year-old needs only $100,000.
CoastFIRE numbers at age 30, 5% real return:
| Target Annual Spending | Target Portfolio (25x) | CoastFIRE Number at 30 |
|---|---|---|
| $40,000 | $1,000,000 | $181,000 |
| $50,000 | $1,250,000 | $226,000 |
| $60,000 | $1,500,000 | $271,000 |
| $80,000 | $2,000,000 | $362,000 |
| $100,000 | $2,500,000 | $452,000 |
Traditional FIRE requires maintaining a high savings rate for 10-20 years. CoastFIRE concentrates the sacrifice into a shorter, more intense period — often your early-to-mid 20s when expenses are naturally lower (no children, smaller housing needs, higher risk tolerance).
A 22-year-old earning $65,000 who saves $25,000/year for 8 years (including employer matches and growth) can realistically accumulate $250,000-$300,000 by age 30 and then coast.
Once you've hit your CoastFIRE number, every job only needs to cover current expenses. This opens up options that traditional career-track thinking forecloses:
The common thread: your income only needs to cover today's bills. Tomorrow's retirement is already funded.
Knowing that your retirement is funded — even if you can't touch it for decades — provides a foundation of financial security that changes how you experience work. Being laid off is stressful but not catastrophic. A bad manager is a problem to solve, not an existential threat. The power dynamic between employee and employer shifts when retirement isn't at stake.
Full FIRE requires 25x current expenses, often $1M-$2M+. CoastFIRE requires $200K-$400K for someone in their late 20s to early 30s. This is ambitious but achievable for a broader range of incomes — particularly for those who start early.
Maya, age 23, graduates with a computer science degree earning $85,000/year.
Phase 1: The Sprint (Ages 23-30)
| Year | Age | Income | Savings | Retirement Balance |
|---|---|---|---|---|
| 1 | 23 | $85,000 | $30,000 | $32,000 |
| 2 | 24 | $90,000 | $33,000 | $68,000 |
| 3 | 25 | $95,000 | $35,000 | $108,000 |
| 4 | 26 | $100,000 | $38,000 | $153,000 |
| 5 | 27 | $105,000 | $40,000 | $203,000 |
| 6 | 28 | $110,000 | $42,000 | $257,000 |
| 7 | 29 | $115,000 | $44,000 | $316,000 |
Savings include 401(k) contributions, employer match, Roth IRA, and taxable brokerage. Assumes 7% returns during accumulation.
At age 29, Maya has $316,000. Her CoastFIRE number for $60,000/year spending at 65 (at 5% real return) is $271,000. She's past her CoastFIRE number.
Phase 2: The Coast (Ages 30-65)
Maya leaves her corporate software job. She:
Meanwhile, her $316,000 portfolio grows untouched:
| Age | Portfolio (5% real) | Portfolio (7% real) |
|---|---|---|
| 30 | $316,000 | $316,000 |
| 35 | $403,000 | $443,000 |
| 40 | $515,000 | $621,000 |
| 45 | $657,000 | $871,000 |
| 50 | $839,000 | $1,222,000 |
| 55 | $1,071,000 | $1,714,000 |
| 60 | $1,367,000 | $2,404,000 |
| 65 | $1,745,000 | $3,371,000 |
At the conservative 5% real return, Maya has $1.75M at 65 — supporting $70,000/year at 4%. At the optimistic 7%, she has $3.37M. Either outcome funds a comfortable retirement, all from savings she made before age 30.
CoastFIRE introduces a specific account challenge: if most of your savings are in tax-advantaged accounts (401(k), IRA), you can't access them penalty-free until 59.5. This is fine for CoastFIRE — you're working until 60-65 anyway — but it means your savings are locked during the coast phase.
Optimal account split for CoastFIRE:
| Account | Purpose During Coast | Purpose at Retirement |
|---|---|---|
| 401(k)/Traditional IRA | Grows untouched | Primary retirement income |
| Roth IRA | Emergency reserve (contributions withdrawable anytime) | Tax-free retirement income |
| Taxable brokerage | Optional buffer for career transitions | Flexible access before 59.5 |
See Account Type Strategy for the full framework. During the sprint phase, maximise tax-advantaged space; during the coast phase, your only financial concern is covering current expenses.
CoastFIRE has its own set of vulnerabilities beyond the general FIRE criticisms.
The entire model rests on compound growth averaging 5-7% real over 30-40 years. While US equities have historically delivered this, it is not guaranteed.
The sensitivity problem:
| Real Return | $300K at 30 → Value at 65 |
|---|---|
| 3% | $845,000 |
| 5% | $1,659,000 |
| 7% | $3,202,000 |
| Historical US average (~6.5%) | $2,735,000 |
The difference between 3% and 7% real return is a factor of 3.8x. A sustained low-return environment (as Japan experienced from 1990-2020) could leave a CoastFIRE follower with far less than planned.
Mitigation: Use conservative assumptions (5% real or lower). If your CoastFIRE number works at 5%, a 7% reality gives you abundance. If you optimistically plan at 7% and get 4%, you're short.
CoastFIRE plans target future portfolio value based on today's spending. But spending changes — children, housing upgrades, healthcare costs as you age, caring for elderly parents. The $60,000 budget at 30 may become $80,000 at 45 even in real (inflation-adjusted) terms due to lifestyle changes.
Mitigation: Target a higher spending level than you currently need, or plan to resume modest saving if spending increases.
Lower-stress, part-time, or freelance work often lacks employer benefits — particularly health insurance and retirement plan access. In the US, this means:
See Medicare Planning and Healthcare for the healthcare dimension.
CoastFIRE assumes you'll continue working in some capacity for 25-35 more years. Health problems, disability, caregiving responsibilities, involuntary job loss, or industry disruption could eliminate your ability to earn. Unlike full FIRE (where the portfolio covers everything), CoastFIRE requires ongoing income for current expenses.
Mitigation: Maintain disability insurance during the coast phase. Keep marketable skills current. Build an emergency fund beyond the retirement portfolio.
Social Security benefits are based on your highest 35 years of earnings. A CoastFIRE person who earns $100K for 8 years and then $55K for 25 years will have a noticeably lower benefit than someone who earned $100K+ for 35 years. Those zero-earning or low-earning years pull the average down.
Practical impact: Maybe $500-$800/month less in Social Security at 67 compared to a full career at higher earnings. Over a 25-year retirement, this is $150,000-$240,000 in lost guaranteed income.
Mitigation: Factor reduced Social Security into your target portfolio. The CoastFIRE portfolio needs to compensate for the lower guaranteed income floor. See Social Security Claiming Strategy.
People who have the discipline to save $30,000-$40,000/year in their 20s often find it psychologically impossible to stop. The habit that got them to CoastFIRE makes the "coast" phase anxiety-inducing. Many CoastFIRE adherents report continuing to save "just a little" — which defeats the purpose.
This isn't a flaw in the strategy but in the execution. It's worth noting because the psychological dimension is often underestimated.
| Dimension | Full FIRE | CoastFIRE | BaristaFIRE | LeanFIRE |
|---|---|---|---|---|
| Savings needed | 25x expenses | ~5-10x expenses (at 25-30) | 15-20x expenses | 25x (low spending) |
| Retirement age | 35-50 | 60-67 | 40-55 (partial) | 35-50 |
| Work after FI | Optional | Required until ~65 | Part-time required | Optional |
| Spending flexibility | High | Moderate | Moderate | Low |
| Healthcare solution | ACA/self-fund | Employer coverage possible | Employer coverage | ACA/self-fund |
| Risk level | Sequence risk | Return assumption risk | Employer risk | Spending shock risk |
| Best for | High earners, work-averse | Young savers, career-changers | Anyone, any income | Minimalists |
CoastFIRE is best suited for people who:
CoastFIRE is poorly suited for people who: