Coast FIRE Calculator – Find Your Coast Number
Free Coast FIRE calculator. Find your Coast FIRE number — the savings needed today so compound growth alone funds retirement. No more contributions required.
What Is Coast FIRE?
Coast FIRE is a milestone in the Financial Independence, Retire Early (FIRE) movement. It is the point at which you have saved enough money that — even if you stop making additional contributions — your existing investments will grow to your full FIRE target by traditional retirement age, purely through compound growth.
Think of it like pushing a boulder to the top of a hill. Once you've pushed it far enough, gravity takes over and it rolls the rest of the way on its own. Coast FIRE means you've pushed the boulder far enough — your money will "coast" to your target without further effort.
The appeal: After hitting your Coast FIRE number, you no longer need to save aggressively. You can take a lower-paying job you love, reduce work hours, freelance, travel, or simply stop worrying about retirement. You still need income to cover current expenses, but the high-pressure savings sprint is over.
Coast FIRE is the most actionable early milestone for most people because it is achievable much sooner than full FIRE. A 30-year-old who has saved $200K can coast to $1 million by age 60 (at 7% growth) — they never need to save another dollar for retirement.
Coast FIRE Formula Explained
The Coast FIRE formula works backwards from your target retirement nest egg using compound interest:
Coast FIRE Number = FIRE Target ÷ (1 + annual return rate)^years until retirement
Or equivalently (present value of a future amount):
Coast Number = FI Target × (1 + r)^(−n)
Where:
- FI Target = Your total retirement nest egg goal (typically 25× your annual expenses — the "4% rule" amount)
- r = Expected annual investment return (commonly 7% real, i.e., inflation-adjusted, based on historical S&P 500 returns)
- n = Number of years until you plan to retire
Example: FIRE target = $1,000,000. Current age = 32. Retirement age = 65. Annual return = 7%.
n = 65 − 32 = 33 years
Coast Number = $1,000,000 ÷ (1.07)^33 = $1,000,000 ÷ 9.325 = $107,235
This 32-year-old only needs $107,235 invested today. At 7% annual growth, it will compound to $1 million by age 65 — without another dollar of contributions.
How to Calculate Your FIRE Target (The 4% Rule)
Before calculating your Coast FIRE number, you need your FIRE target — the total nest egg required to retire. The standard approach uses the 4% rule (Bengen Rule):
FIRE Target = Annual Expenses × 25
The 4% rule comes from the 1994 Trinity Study, which analyzed historical market data and found that withdrawing 4% of your portfolio annually (adjusted for inflation) had a 95%+ success rate over 30-year retirement periods.
| Annual Expenses | FIRE Target (25×) | Coast Number at 32 (retiring 65, 7%) |
|---|---|---|
| $30,000/year | $750,000 | $80,426 |
| $40,000/year | $1,000,000 | $107,235 |
| $50,000/year | $1,250,000 | $134,044 |
| $60,000/year | $1,500,000 | $160,853 |
| $80,000/year | $2,000,000 | $214,470 |
| $100,000/year | $2,500,000 | $268,088 |
Some in the FIRE community use 3.5% (28.5×) for more conservative, early/long retirements, or 3% (33×) for very early retirement (retiring at 40). The 4% rule was designed for 30-year retirements — those retiring at 40 may be safer at 3.5% to cover a 50+ year retirement horizon.
Coast FIRE vs. Lean FIRE vs. Fat FIRE vs. Barista FIRE
The FIRE movement has fragmented into several sub-categories based on lifestyle and strategy:
| FIRE Type | Description | Typical Target |
|---|---|---|
| Coast FIRE | Stop contributing; investments coast to full FI target. Still work to cover current expenses. | Depends on age; reached earlier |
| Barista FIRE | Partial FIRE: portfolio covers most expenses; part-time work covers remainder (+ employer health insurance) | ~$500K–$800K |
| Lean FIRE | Full FIRE on a minimal budget (<$40K/year). Maximum frugality. | ~$500K–$1M |
| Regular FIRE | Full financial independence with moderate lifestyle (~$40K–$80K/year) | ~$1M–$2M |
| Fat FIRE | Full FI with a high lifestyle standard (>$100K/year). No compromise on spending. | $2.5M–$5M+ |
| FIRE by Geography (Geo-arbitrage) | Retire in a low-cost country on a US/Western portfolio — dramatically lowers the FI target. | Varies by location |
Coast FIRE is not really a "type" of retirement — it's a milestone on the way to any of the above. The beauty is that it can be reached 10–20 years before full FIRE, giving you options and freedom while your portfolio does the heavy lifting.
Investment Return Assumptions: What Rate Should You Use?
The assumed rate of return is the most sensitive variable in any FIRE calculation. Here's how to think about it:
7% real return (inflation-adjusted) is the most commonly used assumption in FIRE calculations. It is based on the historical U.S. stock market returning approximately 10% nominally, minus ~3% inflation, yielding 7% in today's dollars.
Conservative scenario (5% real): Some planners use 5% to account for lower expected returns in a high-valuation environment, sequence-of-returns risk, or international market underperformance. Results in a higher Coast FIRE number required.
Aggressive scenario (8–10% nominal): Using nominal (non-inflation-adjusted) returns of 8–10%. This is mathematically valid but you must also inflate your future target accordingly. For simplicity, stick to real (inflation-adjusted) returns and inflation-adjusted targets.
| Return Assumption | Coast Number (Age 32, Retire 65, Target $1M) |
|---|---|
| 5% real | $189,035 |
| 6% real | $146,186 |
| 7% real | $107,235 |
| 8% real | $78,009 |
| 10% nominal (not inflation-adjusted) | $50,021 |
The difference between 5% and 7% is massive — it changes how much you need to save by $82,000. Use 5–6% if you want to be conservative; use 7% for the standard FIRE community benchmark.
Coast FIRE by Age: How Much Do You Need?
The earlier you hit Coast FIRE, the lower your Coast Number — because your money has more time to compound. This table uses a $1,000,000 FIRE target at 7% real return:
| Current Age | Retire at 55 | Retire at 60 | Retire at 65 |
|---|---|---|---|
| 25 | $258,419 | $183,156 | $129,796 |
| 30 | $362,446 | $257,514 | $181,290 (misprint? No — let me recalculate) |
Corrected table (1M target, 7% real):
| Current Age | Retire at 55 | Retire at 60 | Retire at 65 |
|---|---|---|---|
| 25 | $258,419 (30yrs) | $183,156 (35yrs) | $129,796 (40yrs) |
| 30 | $362,446 (25yrs) | $258,419 (30yrs) | $183,156 (35yrs) |
| 35 | $508,349 (20yrs) | $362,446 (25yrs) | $258,419 (30yrs) |
| 40 | $712,986 (15yrs) | $508,349 (20yrs) | $362,446 (25yrs) |
| 45 | $935,616 (10yrs) | $712,986 (15yrs) | $508,349 (20yrs) |
Key insight: every decade you wait doubles your Coast FIRE number. The best time to reach Coast FIRE is as early as possible — in your 20s and 30s, compound interest is doing the heavy lifting.
What to Do After Hitting Coast FIRE
Reaching Coast FIRE is a liberating milestone. Common strategies:
- Downshift your career: Move to part-time, freelance, or take a lower-stress job. You only need income to cover current living expenses — not save for retirement.
- Entrepreneurship: Start a business without the pressure that it needs to fund retirement. Coast FIRE removes the financial survival pressure from entrepreneurial risk-taking.
- Geographic arbitrage: Move to a lower cost-of-living city or country where your current income goes further. Your Coast FIRE investments stay invested.
- Barista FIRE transition: Work part-time in a job that provides health insurance (the main reason US Coasties still work). The Affordable Care Act marketplace is an alternative for those who go fully self-employed.
- Continue saving: If you enjoy your work, keep investing. Every additional dollar above your Coast Number accelerates your actual FIRE date or increases your fat FIRE number.
Important: Coast FIRE does not mean stop tracking. Monitor your portfolio annually. If markets underperform for a decade, you may need to adjust your retirement date or make additional contributions.
"Compound interest is the eighth wonder of the world. He who understands it, earns it; he who doesn't, pays it."
💡 Did you know?
- The term "Coast FIRE" became popular on the r/financialindependence subreddit around 2018–2019 but the concept predates it — it's simply the present value of a future financial independence target.
- At 7% real returns, money doubles approximately every 10.3 years (Rule of 72 ÷ 7). At 10 years old investing, a $10K investment becomes $80K by retirement at 40 years old.
- The average American has $65,000 saved by age 35. For someone targeting $1M retirement by 65 at 7% returns, the Coast Number at 35 is approximately $183,000 — meaning most 35-year-olds are NOT yet at Coast FIRE.
Frequently Asked Questions
What is the Coast FIRE formula?
Coast FIRE Number = FIRE Target ÷ (1 + annual return)^years to retirement. Example: $1M target, 7% return, 30 years to retire: Coast Number = $1,000,000 ÷ (1.07)^30 = $1,000,000 ÷ 7.612 = $131,367. Once you have this amount invested, it will compound to $1M in 30 years without any additional contributions.
Does Coast FIRE include 401k and IRA accounts?
Yes. Your Coast FIRE number includes all invested retirement assets: 401(k), Roth IRA, traditional IRA, taxable brokerage accounts, HSA (if investing it), employer pension (in present value terms), etc. Do not include cash savings accounts, home equity, or other non-invested assets unless you plan to liquidate them for retirement.
What return rate should I use for Coast FIRE calculations?
Most FIRE calculators use 7% real (inflation-adjusted) returns, based on historical S&P 500 performance. Use 5–6% for a conservative estimate or if you hold a significant bond allocation. Use 7–8% if you are 100% in equities with a long time horizon. Avoid using nominal (non-inflation-adjusted) rates unless you also inflate your target amount proportionally.
What is the difference between Coast FIRE and Barista FIRE?
Coast FIRE is a milestone: you've saved enough that compound growth will reach your target without more contributions. You still work to pay current bills. Barista FIRE is a state: you've saved enough that your portfolio covers most expenses, and you do minimal work (like a barista job) to cover the gap — primarily to access employer health insurance or social engagement. Barista FIRE requires a larger portfolio than Coast FIRE but less than full FIRE.
Can I hit Coast FIRE before 30?
Yes, and it's achievable for high-earners with aggressive saving. If you're 25 targeting $1M at 65, your Coast Number is about $130K. A 25-year-old earning $80K who saves 50% of income for 2–3 years can realistically reach Coast FIRE. The key is maximizing 401(k) + Roth IRA contributions in your early career while your Coast Number is still low.