What is the 4% rule in FIRE?

The 4% rule (from the 1998 Trinity Study) says you can safely withdraw 4% of your portfolio annually in retirement and not run out of money over a 30-year period, based on historical US market returns. Your FI Number is therefore 25× your annual spending (annual spend ÷ 0.04).

What is Lean FIRE vs Fat FIRE?

Lean FIRE targets a frugal retirement lifestyle — often $25,000/year or less — requiring a smaller portfolio (≈$625,000). Fat FIRE targets a comfortable or luxurious lifestyle, often $100,000+/year, requiring $2.5M or more. Standard FIRE is in between, typically matching current spending.

Is a 3% safe withdrawal rate better than 4%?

A 3% SWR significantly reduces failure risk, especially for retirements longer than 30 years (early retirees at 40 might need 50+ years of portfolio longevity). The tradeoff is a larger required portfolio (33× spending vs 25×). Many FIRE practitioners use 3.5% as a middle ground.

FIRE Calculator — Years to Financial Independence

Q: What is Coast FIRE?

Coast FIRE is the point where your existing portfolio, left to grow without any new contributions, will reach your FI Number by a conventional retirement age (typically 65). Once you hit Coast FIRE, you only need to earn enough to cover current living expenses — you can stop investing aggressively.

Q: How does savings rate affect years to retirement?

Savings rate has a dramatic effect — it both reduces the spending you need to replace and increases the capital you accumulate. Saving 10% of income typically requires ~40 years to FI. Saving 50% takes ~17 years. Saving 70% takes ~8.5 years. These numbers assume a 7% real return and starting from zero.

Your Numbers

Current age

Current portfolio / savings

Annual income (after-tax take-home)

Current annual spending

Annual savings contribution

Auto-computed: income − spending. Edit to override.

Target retirement spending / year

Defaults to current spending. Change for Lean/Fat scenarios.

Expected annual return (%)

7% = historical real return (inflation-adjusted). 10% = nominal.

Safe withdrawal rate (%)

4% = Trinity Study baseline. 3–3.5% = conservative for 40+ year retirement.

Show in real (inflation-adjusted) terms

Your FIRE Results

Years to Financial Independence

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FI Number

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FI Date

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Savings Rate

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FI Age

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FI Number (spending × multiplier)$—
Current portfolio$—
Gap to close$—
Annual contribution$—

🏖 Coast FIRE: Calculating…

What if I save an extra $X/month?

$ /mo

Enter an amount above to see the impact.

Portfolio Growth Projection

Age	Year	Portfolio Value	FI Progress

Savings Rate → Years to FI

Based on your inputs, here's how changing your savings rate affects your timeline. Assumes 7% real return, starting from your current portfolio.

Savings Rate	Years to FI	FI Date

Return Rate Sensitivity

How the 4% Rule Works

The 4% rule comes from the 1998 Trinity Study, which analyzed historical US stock and bond returns from 1926 to 1995. It found that a portfolio of 50–75% stocks could sustain annual withdrawals of 4% for 30 years with a very high success rate (95%+).

Your FI Number is simply the inverse: annual spending ÷ 4% = 25× annual spending. If you spend $50,000/year, you need $1,250,000. If you spend $40,000/year, you need $1,000,000.

FI Number = Annual Spending ÷ Safe Withdrawal Rate = Annual Spending × (1 / SWR) = Annual Spending × 25 (at 4% SWR) Portfolio Growth: FV = PV × (1 + r)^n + PMT × ((1 + r)^n − 1) / r where PV = current portfolio, r = annual return, n = years, PMT = annual contribution Coast FI Number = FI Number / (1 + r)^(retirement_age − current_age)

Lean FIRE vs Standard FIRE vs Fat FIRE

Lean FIRE ($25k/yr): Extremely frugal early retirement. FI Number ≈ $625,000. Requires geographical arbitrage, low-cost-of-living area, or minimalist lifestyle. Common in r/leanfire community.
Standard FIRE (match current spending): The default. Retire with the same lifestyle you have today. FI Number depends entirely on your current expenses.
Fat FIRE ($100k/yr): Comfortable, lifestyle-rich retirement. FI Number ≈ $2.5 million. More buffer, more security, but requires either higher income or longer time horizon.

Why Savings Rate Matters More Than Income

The math of FIRE is counterintuitive: it's not how much you earn, it's how much of it you keep. A person earning $150,000 and spending $120,000 (20% savings rate) takes longer to reach FI than someone earning $60,000 and spending $30,000 (50% savings rate). Savings rate simultaneously controls how fast your portfolio grows and how large a portfolio you need.

Coast FIRE Explained

Coast FIRE is the point where your portfolio, left alone with no new contributions, will compound to your FI Number by a conventional retirement age (typically 65). Once you hit Coast FIRE, you can "coast" — work just enough to cover current expenses without needing to invest more. It's a milestone before full FI that many people find psychologically meaningful.

Frequently Asked Questions

What is the 4% rule?

The 4% rule states you can safely withdraw 4% of your portfolio annually in retirement without running out of money over a 30-year period, based on historical US market returns (Trinity Study, 1998). Your FI Number = 25× your annual spending.

What is the difference between Lean FIRE and Fat FIRE?

Lean FIRE targets a very frugal retirement (~$25,000/year), requiring a $625,000 portfolio. Fat FIRE targets a comfortable lifestyle ($100,000+/year), requiring $2.5M+. Standard FIRE matches your current spending.

What is Coast FIRE?

Coast FIRE is when your existing portfolio will compound to your FI Number by retirement age (65) without any new contributions. You've saved enough — now you just need to cover current living costs.

What investment return should I use?

7% is the commonly cited long-run real (inflation-adjusted) return for broad US index funds. For nominal returns use ~10%. Using real returns (7%) means your FI Number is already in today's dollars — no extra inflation adjustment needed.

How does savings rate affect years to retirement?

Dramatically. Saving 10% requires ~40 years to FI. Saving 25% takes ~32 years. Saving 50% takes ~17 years. Saving 75% takes ~7 years. Both the accumulation speed and the lower FI target (less to replace) work together.

Is 3% safer than 4%?

Yes — a 3% SWR (33× spending) significantly reduces failure risk for retirements exceeding 30 years. For someone retiring at 35, who may need 60+ years of portfolio longevity, 3–3.5% is more prudent than 4%.

Ready to Start Investing Toward FI?

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