Coast FIRE Calculator
Find the Coast FIRE number — the nest egg today that grows to your retirement target with zero further contributions.
Coast FIRE = the portfolio you need today that, with zero future contributions, grows into your full FIRE number by retirement. Uses real returns (nominal return minus inflation) so the spending figure stays in today's dollars. Real-world returns vary; use a conservative 4–6% for planning.
The Coast FIRE formula
The math is a single line — compound growth run backward.
Coast FIRE number = FIRE target / (1 + real return)^years to retirement
- FIRE target = annual retirement spending / safe withdrawal rate (e.g. $60,000 / 0.04 = $1,500,000)
- Real return = nominal return − inflation (historically ~6–7% for US equities)
- Years to retirement = retirement age − current age
A worked example
You’re 32, you want to retire at 65, and you plan to spend $60,000/year in retirement:
- FIRE target at 4% withdrawal = $60,000 / 0.04 = $1,500,000
- Years to compound = 65 − 32 = 33 years
- Coast FIRE number at 5% real return = $1,500,000 / (1.05)^33 = $304,000
If you have $304k invested today, you can stop saving — compounding at 5% real for 33 years turns it into $1.5M (in today’s dollars). You still need income to cover current life, but retirement is paid for.
Why Coast FIRE matters more than FIRE for most people
Full FIRE requires 25× annual expenses in liquid assets today. That’s a huge number for almost everyone — $1.5M to retire on $60k/year. Coast FIRE reframes the problem: you only need a fraction of that number, as long as you have time on your side.
The fraction shrinks dramatically with each extra year:
| Years to retire | Coast FIRE % of FIRE target (5% real) |
|---|---|
| 40 | 14% |
| 35 | 18% |
| 30 | 23% |
| 25 | 30% |
| 20 | 38% |
| 15 | 48% |
| 10 | 61% |
| 5 | 78% |
A 25-year-old needs less than a seventh of what a 55-year-old needs to hit Coast FIRE, because the 25-year-old has 40 more years of compounding runway.
What Coast FIRE enables
- Quit a high-paying, high-stress job for lower-paying, meaningful work. Your current income only needs to cover current expenses, not future savings.
- Take a career sabbatical. The portfolio grows on its own while you’re not contributing.
- Switch to freelance or entrepreneurship with less financial anxiety.
- Downshift to part-time (Barista FIRE). Cover groceries with a 20-hour-a-week job; let compounding handle retirement.
Caveats — Coast FIRE is not full FIRE
You still need income to cover today’s expenses — rent, food, insurance, transport. Losing your job at age 35 Coast-FIRE doesn’t mean retirement is guaranteed if you can’t pay rent to age 65 along the way. Sequence-of-returns risk also matters: a prolonged bear market in the first decade after reaching Coast FIRE can dent the compounding path. Most Coast FIRE planners either keep a cash buffer or stay flexible on the retirement age.
Conservative adjustments
- Use a lower real return (4% instead of 6%) to build in a margin of safety.
- Use a lower withdrawal rate (3.25–3.5%) if your retirement horizon is 40+ years.
- Recalculate annually — if markets crash early, your Coast FIRE status may reverse temporarily; stay flexible.
Frequently asked questions
- What is Coast FIRE?
- **Coast FIRE** is the financial milestone where you've invested enough that, without adding another dollar, the balance alone compounds into your full retirement number by the time you retire. You still need a job to cover current expenses, but you no longer need to save. It's "coasting" — your future retirement is handled, and anything you save beyond this point is optional acceleration or lifestyle inflation.
- How is Coast FIRE different from FIRE or Lean FIRE?
- Classic **FIRE** (Financial Independence, Retire Early) means you have enough invested that you can fully stop working today — typically 25× your annual expenses. **Coast FIRE** is a much lower bar: you've front-loaded enough that compound growth does the rest. **Lean FIRE** is regular FIRE but with a very low annual spend (~$25–40k). **Barista FIRE** is Coast FIRE's cousin — you cover expenses with a low-stress part-time job while investments compound untouched.
- Why use "real returns" instead of nominal?
- The calculator asks for **real return** (return after inflation) because the FIRE target is expressed in today's dollars. If you use a nominal return like 10% without subtracting 3% inflation, you'll wildly understate the nest egg needed — compounding nominal growth makes the future look rich, but that future wealth buys less. Historical US equities returned about **6–7% real**. A conservative 4–5% real return is reasonable for long-term planning.
- What withdrawal rate should I use?
- The classic "4% rule" comes from the **Trinity Study** of US markets — a 4% initial withdrawal, inflation-adjusted annually, survived virtually all 30-year historical periods. Modern research (Bengen's own follow-ups, Kitces) suggests 4% is conservative and 4.5–5% is often safe. For longer retirements (45+ years as is common in early retirement), **3.25–3.5%** is the safer range. Adjust up if you have flexibility in spending, down if you don't.
- Is Coast FIRE realistic?
- Yes, and it's often the most achievable FIRE variant. If you invest aggressively in your 20s and early 30s, a modest nest egg can Coast-FIRE with 30+ years of compounding left. Example: at 30 years old aiming for a $1.5M FIRE target at age 65 with 5% real returns, Coast FIRE requires about **$272k invested today** — ambitious but nowhere near the full $1.5M. Save hard early, let compounding take over.
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