What Is My FIRE Number? How to Calculate Early Retirement

Updated March 2026 · 11 min read · By Travis Cook

FIRE (Financial Independence, Retire Early) boils down to one idea: save and invest enough that your portfolio can fund your life forever. No job required. The investment returns without needing a paycheck. The number you need to reach is your "FIRE number," and the math behind it's surprisingly straightforward.

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The 25x Rule: The Foundation of FIRE

Your FIRE number is 25 times your annual expenses. That's it. If you spend $40,000 per year, your FIRE number is $1,000,000. If you spend $60,000 per year, you need $1,500,000. If you can live on $30,000, you only need $750,000.

25x is just the 4% rule flipped around. The Trinity Study found that a stock/bond portfolio can handle 4% annual withdrawals (adjusted for inflation each year) for at least 30 years with a high probability of success. Since 1 / 0.04 = 25, you need 25 times your annual spending to safely withdraw 4% per year.

Your Savings Rate Is Everything

Your savings rate matters more than your salary. Someone earning $200K who spends $180K (10% savings rate) will take way longer to reach FIRE than someone earning $80,000 who spends $40,000 (50% savings rate). Higher savings rates work a double magic: you save more money each year and you need less money in total because your expenses are lower.

Savings Rate	Years to FIRE	Key Insight
10%	51 years	Standard retirement timeline
25%	32 years	Retire a few years early
50%	17 years	The sweet spot for most FIRE seekers
65%	10.5 years	Aggressive but achievable for high earners
75%	7 years	Extreme frugality or very high income

These assume 5% real returns and starting from zero. Your actual timeline will differ based on your starting balance and investment returns.

The Types of FIRE

Traditional FIRE

Standard FIRE: 25x your annual expenses. You're done working forever. Most people target somewhere between $750,000 and $2,000,000 depending on their lifestyle and location.

Lean FIRE

Lean FIRE: financial independence on a tight budget, usually under $40K/year in expenses. FIRE number below $1,000,000. It's more achievable but requires maintaining a frugal lifestyle indefinitely. People who pursue Lean FIRE often live in low-cost-of-living areas, and some move abroad to stretch their dollars further.

Fat FIRE

Fat FIRE: financial independence without sacrificing lifestyle. $100K+/year in expenses, meaning $2.5M+ saved. Common among high-income professionals (doctors, lawyers, tech workers) who want to retire early without downsizing their lifestyle.

Barista FIRE

Barista FIRE: your portfolio covers most expenses, but you work part-time for the gap and (critically) health insurance. The name comes from the idea of working at a coffee shop (Starbucks famously offers health insurance to part-time employees). This is an attractive middle ground for people who want to leave their career but aren't quite at full financial independence.

Coast FIRE

Coast FIRE: you've invested enough that compounding alone gets you to full FIRE by 60-65, even if you never add another dollar. Once you hit your Coast FIRE number, you only need to earn enough to cover current living expenses. No more saving required. This is a powerful psychological milestone because it eliminates the stress of "falling behind" on retirement savings.

Example: Coast FIRE at age 30

If you've $200,000 invested at age 30 and expect a 7% real return, that money will grow to roughly $1,500,000 by age 60 without adding a single dollar. If your expected retirement spending is $60,000 per year ($1,500,000 / 25), you've already hit Coast FIRE.

How Compound Interest Powers FIRE

The math works because of compounding. Early on, your contributions do the heavy lifting. Later, investment returns take over and do most of the work. A $500,000 portfolio earning 7% generates $35,000 in returns in a single year. At $1,000,000, that's $70,000. Eventually, your money makes more money in a year than you can save from your salary.

This is why starting early is so powerful, and why the Compound Interest Calculator is such a useful tool for FIRE planning. Even small contributions in your 20s have decades to compound.

Where to Put Your FIRE Money

The FIRE investment strategy is boring on purpose: low-cost index funds. A total U.S. stock market index fund (like VTSAX or VTI) combined with an international index fund gives you broad diversification at minimal cost. Many FIRE adherents follow a "three-fund portfolio" of U.S. stocks, international stocks, and bonds.

Tax-advantaged accounts should be maximized first: 401(k) (up to $24,500 in 2026, or $32,500 if over 50, or $35,750 if 60-63), Roth IRA ($7,500, or $8,600 if over 50), and HSA ($4,400 individual, $8,750 family in 2026). After maxing these, invest in a taxable brokerage account. The Retirement Calculator can help you project growth across these accounts.

Common FIRE Mistakes

Forgetting healthcare. Insurance without an employer is brutal in the US. ACA plans run $300-800+/month depending on age and location. Budget for this before declaring yourself financially independent.

Assuming 10% returns forever. That's nominal, not real. Use 5-7% after inflation for projections.

Ignoring withdrawal taxes. Traditional 401(k) and IRA money gets taxed as income when you pull it out. A Roth conversion ladder or other tax-efficient withdrawal strategy is important for early retirees.

Assuming flat expenses. What you spend at 35 won't be what you spend at 55. Children, health care, travel, and housing costs can shift significantly.

Run Your FIRE Scenario

See how savings rate, return assumptions, and expenses affect your FIRE timeline.

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About the Author

Travis Cook covers personal finance for MayoCalc, building tools and guides backed by data from the Federal Reserve, IRS, and major financial institutions. All figures are verified against primary sources and updated annually.

FIRE FAQ

What is a good FIRE number?

Your FIRE number is 25 times your annual expenses. For someone spending $40,000 per year, the target is $1,000,000. For $60,000 in annual spending, it's $1,500,000. The "right" number depends entirely on your lifestyle and cost of living.

Is the 4% rule still valid?

The original Trinity Study found that a 4% withdrawal rate had a high probability of lasting 30 years based on historical returns. Some recent research suggests 3.5% may be more appropriate given lower expected future returns and longer retirement horizons for early retirees. Many FIRE adherents use 3.5-4% as their planning range.

How long does it take to reach FIRE?

It depends almost entirely on your savings rate. At a 50% savings rate with a 5% real return, it takes about 17 years starting from zero. At 25%, it takes about 32 years. At 65%, about 10.5 years. Use the FIRE Calculator to model your specific situation.

What about Social Security?

Social Security is a bonus for early retirees, not the foundation. If you retire at 40, you've 22 years before you can claim at 62 (with a reduced benefit) or 27 years before full retirement age at 67. Many FIRE planners calculate their number without Social Security and treat it as a safety margin.

Can I pursue FIRE with a normal income?

Absolutely. FIRE is more about spending less than about earning more. Someone earning $60,000 who saves 50% ($30,000 per year) will reach FIRE faster than someone earning $150,000 who saves 15% ($22,500 per year). Reducing housing costs, transportation costs, and food spending are the three biggest levers for most people.

What is the difference between FIRE and regular retirement?

Traditional retirement planning assumes you work until 65-67 and then live on Social Security plus savings. FIRE is about accumulating enough that work becomes optional at a much younger age, often in your 30s, 40s, or 50s. The math is the same (compound interest + withdrawal strategy), but the timeline is compressed.

Track Your Savings Rate With CMS Flow

Your savings rate is the most important number on the path to FIRE. CMS Flow is a free budgeting app that makes it easy to see your income, expenses, and exactly how much you're saving each month.

For more on this topic, see our retirement savings benchmarks by age.

For more on this topic, see our compound interest guide.

For more on this topic, see our average 401(k) balance by age.

Sources

Trinity Study (Cooley, Hubbard, Walz): Original research behind the 4% withdrawal rule

Related Tools

Calculate your FIRE timeline with the FIRE Calculator (or try the Advanced FIRE Calculator for historical backtesting). See how contributions grow over time with the Compound Interest Calculator. Plan for traditional retirement with the Retirement Calculator. Set and track a target with the Savings Goal Calculator. Calculate your take-home pay in any state with the Paycheck Calculator.

Disclaimer: This article is for educational purposes only and does not constitute financial advice. Investment returns are not guaranteed, and past performance does not predict future results. The 4% rule is based on historical data and may not apply in all market conditions. Consult a qualified financial advisor for personalized retirement planning.