Financial independence (FIRE) calculator

The FIRE number, in one sentence

Financial Independence (FI) is the point at which your investment portfolio is large enough that it can support your lifestyle indefinitely from returns alone — no salary required. The classic formula: FI number = annual expenses × 25. That's the inverse of the 4% safe withdrawal rate popularized by the 1998 Trinity Study, which found that a portfolio of 60% stocks and 40% bonds withdrawn at 4% per year (inflation-adjusted) would last at least 30 years in 96% of historical periods.

Spend $50,000 a year? FI number is $1.25M. Spend $100,000? It's $2.5M. The power of this framework is that the math cuts both ways — lowering expenses by $10K per year lowers your FI target by $250K and raises your savings rate at the same time.

Why savings rate is the only variable that matters

In 2012, Mr. Money Mustache published a table that changed the early-retirement movement: given constant after-tax income and expenses, the years to financial independence depends only on your savings rate — not on your actual income. From zero assets, assuming 5% real returns:

• 10% savings rate: 51 years to FI
• 15% savings rate: 43 years
• 20% savings rate: 37 years
• 25% savings rate: 32 years
• 35% savings rate: 25 years
• 50% savings rate: 17 years
• 65% savings rate: 11 years
• 75% savings rate: 7 years

Why the dramatic acceleration? Because raising your savings rate does two things at once: it grows the portfolio faster, and it lowers the target (because the denominator — annual expenses — is smaller). A 50% saver needs less portfolio than a 10% saver because they live on less.

The flavors of FIRE

FIRE stands for Financial Independence, Retire Early. It's not one single movement — it splits into several sub-philosophies:

• Lean FIRE: FI with $25K–$40K/year expenses. FI number: $625K–$1M. Requires deliberately frugal living, often with geographic arbitrage (lower-cost cities or countries). Common in online FIRE communities.
• Regular FIRE: $50K–$80K/year expenses. FI number: $1.25M–$2M. Mostly middle-class lifestyle, intentional spending, solid saver but not extreme.
• Fat FIRE: $100K+/year expenses. FI number: $2.5M+. Retire with a high standard of living — nice house, regular travel, fewer compromises.
• Barista FIRE: Reach the point where part-time work covers expenses and your portfolio compounds untouched. Typically around 50–75% of a full FI number.
• Coast FIRE: Front-load savings in your 20s–30s so that, without adding another dollar, the portfolio compounds into a full FI number by age 60–65. Work after that point is optional for lifestyle, not for retirement.
• Slow FI: Stay in meaningful work and use the freedom FI provides (fewer hours, sabbaticals, career switches) rather than stopping entirely.

Is 4% still the right withdrawal rate?

The Trinity Study used 30 years of retirement — fine for traditional retirees starting at 65 but short for someone retiring at 40. Updated research (especially Early Retirement Now's detailed simulations) suggests 3.25–3.5% is safer for 50-year retirements, especially if you start in a period of elevated valuations.

The calculator lets you set withdrawal rate so you can see sensitivity:

• 4% rate: 25× expenses. Canonical FIRE. Safe for ~30 years.
• 3.5% rate: 28.5× expenses. Recommended for 40–50 year retirements.
• 3% rate: 33× expenses. Very conservative; essentially endowment-style perpetual withdrawal.
• 5% rate: 20× expenses. Viable with flexibility, part-time income, or Social Security cushion.

Most people also forget that Social Security exists. A 40-year-old retiring with $1.5M who also expects $30K/year in Social Security at 67 has way more margin than pure FI math suggests. Running the numbers strictly from portfolio-only is conservative.

How real returns work

The real returnis nominal return minus inflation. Historical real return on a 60/40 portfolio is roughly 5–7%. The calculator uses real return throughout, meaning all figures are in today's dollars. You don't need to separately inflate expenses or the FI number — real-return math does that for you.

Historical context: the S&P 500 averaged about 10% nominal / 7% real since 1928. Long-term bond returns averaged 2–3% real. A 100% stock portfolio might earn 6–7% real long-term. A 60/40 mix earns about 5%.

The math behind "coast FI"

Coast FI is the amount you need today to hit a full FI number by traditional retirement age without adding another dollar. For a target FI number of $1.5M and a 30-year horizon at 5% real returns:

Coast FI = $1,500,000 ÷ (1.05)^30 = $347,000

Someone in their 30s with $347K in a low-cost index portfolio can quit saving entirely and still retire comfortably at 65 — as long as the market delivers roughly its historical average. Coast FI is a popular halfway milestone because it offers psychological freedom (you no longer have to save) while still requiring ongoing work to cover current expenses.

Common pitfalls

Forgetting about healthcare

Pre-Medicare (before 65), health insurance for an early retiree can run $15K–$25K/year for a couple on an ACA marketplace plan, more without subsidies. Many early retirees deliberately structure Roth conversions to keep AGI low and qualify for maximum ACA subsidies. Include healthcare in your expense estimate or your FI number will be too low.

Assuming expenses stay flat

Kids, aging parents, and lifestyle drift all push expenses up over time. Inflation is separately handled by using real returns. But real lifestyleinflation (nicer travel, bigger house) isn't. Be honest about whether your $50K/year budget will hold at 55 and 75, not just 35.

Sequence-of-returns risk

A 40% market drop in year one of retirement is devastating in a way that the same drop in year 15 isn't — you're selling depleted assets to fund living expenses. The 4% rule survives most sequences historically, but not all. Mitigations: 1–2 years of expenses in cash/bonds, flexible spending in down years, part-time income for the first few years.

Taxes in retirement

Your $60K/year retirement budget is spending, not pre-tax income. In a Traditional 401(k) you need to withdraw about $72K to spend $60K (at a 17% effective rate). Roth withdrawals are tax-free. A taxable brokerage at long-term capital gains rates is often the most tax-efficient of the three. The common strategy: build a mix of all three "tax buckets" so you can manage taxable income bracket-by-bracket in retirement.

Ignoring non-monetary returns to work

Post-FIRE regret is real. Many early retirees report that the first six months are bliss and the next year is hollow. Work provides structure, identity, and social connection that money alone doesn't replace. The healthiest FIRE plans have a clear picture of what retirement looks like, not just what it costs.

Step-by-step: getting to FI

1. Know your actual expenses. Track them for 12 months minimum. Use the 50/30/20 budget and subscription audit to accurately count.
2. Compute your savings rate. Annual savings ÷ after-tax income. Anything under 15% is slow. 30% is real progress. 50%+ is aggressive.
3. Max tax-advantaged accounts first. 401(k) match, HSA, Roth IRA, then rest of 401(k), then taxable brokerage. See the paycheck calculator and Roth vs Traditional analysis.
4. Invest it all in low-cost index funds. Vanguard VTSAX, Fidelity FZROX, Schwab SWTSX — pick one, stop worrying. Expense ratios matter enormously over 30 years; 1% vs 0.05% in fees is the difference between $1M and $1.3M.
5. Avoid lifestyle inflation. Every raise: 50% to lifestyle, 50% to savings, minimum. Ratchet the savings side up each year.
6. Revisit annually. Expenses change, income changes, portfolio changes. A simple yearly check-in keeps you honest.

Related calculators

• Retirement calculator — same math with traditional retirement framing.
• Compound interest calculator — see the raw power of each dollar saved.
• Net worth calculator — the status check against your FI number.
• 50/30/20 budget — lowers expenses and raises savings rate simultaneously.

FAQ

Does Social Security count toward my FI number?

Yes, though conservatively. A common approach is to ignore SS for the first calculation (to stay safe), then run a second scenario assuming 70–80% of projected benefits. At current law, someone claiming $30K/year in benefits effectively replaces $750K of portfolio — that's a lot of cushion.

What if I have a pension?

Similar treatment to Social Security. A $40K/year pension at 4% withdrawal is equivalent to $1M of portfolio. Include it as a reduction from your required FI number.

Is this possible on a median income?

Yes, but slowly. A single earner making $65K with $45K/year expenses and a 30% savings rate reaches Lean FI ($1.1M) in about 23 years with historical returns. Faster with raises, slower with lifestyle creep. Dual-income households can get there in half the time.

What's the catch?

The catch is that it requires you to seriously reduce your spending relative to peers, sustain that for a decade or two, and invest consistently through scary market periods. Most people don't want to, which is fine — but it's the reason the FIRE movement has more books than practitioners.