FIRE Calculator

How to use this calculator

Enter your current age, target retirement age, current savings, monthly investment, expected annual retirement expenses, expected return, and inflation rate. Click Calculate FIRE.

Annual Retirement Expenses is the most important input. Get this wrong and everything else is off. Pull 12 months of bank and credit card statements. Most people underestimate by 15% to 25% when working from memory. If you can’t remember what you spent last year, the number you guess is probably too low.

Expected Return is your assumed annual portfolio return. 7% is reasonable for a diversified equity-heavy portfolio over a long horizon. Use real returns (net of inflation) if you want everything in today’s dollars, or nominal returns if you want future dollar figures.

Inflation Rate adjusts the FIRE number calculation so your target stays in purchasing power terms. 3% is the US historical average.

The results show your FIRE number, projected portfolio at your target retirement age, progress percentage, and how the three main FIRE variants compare at your expense level.

The core formula

FIRE math starts with one equation:

Spend $60,000 per year and you need $1,500,000.

The 4% comes from the Trinity Study, published in 1998 by three finance professors at Trinity University in Texas. They analyzed every 30-year retirement period from 1926 to 1995 and found that a portfolio of roughly 60% stocks and 40% bonds, with 4% withdrawn annually and adjusted for inflation each year, survived every single historical period.

The 25x multiplier is just the inverse: 1 ÷ 0.04 = 25. You need 25 times your annual spending.

What the FIRE number actually means

The FIRE number isn’t a pile of money you spend down to zero. A $1.5M portfolio at 4% withdrawal generates $60,000 per year indefinitely in theory, because the portfolio’s earnings refill what you take out.

At 7% nominal return and 3% inflation, the real return is about 3.9%. You withdraw 4%, which exceeds the real return slightly. But the portfolio is drawing from a larger base each year, and markets don’t return exactly 3.9% every year. Good years rebuild the buffer that bad years erode.

The 4% rule failed in only about 5% of 30-year historical scenarios. Those failures were mostly retirements starting in the late 1960s, right before the stagflation decade of the 1970s: high inflation, mediocre stock returns, and a brutal sequence of years to start from.

Your savings rate is the lever that matters

How fast you reach FIRE depends on one thing more than anything else: your savings rate. The relationship is non-linear and dramatic.

Savings Rate	Years to FIRE (from scratch)
10%	~43 years
20%	~37 years
30%	~28 years
40%	~22 years
50%	~17 years
60%	~12.5 years
70%	~8.5 years

Assumes 5% real return, starting from zero, and that your spending in retirement matches your current spending (which it roughly should, since saving more means spending less).

The acceleration at high savings rates happens because two things improve simultaneously: you’re adding more each month, and your required FIRE number is smaller. You spend less, so you need less to sustain that lifestyle. Both effects compound.

A household earning $120,000 and saving 20% ($24,000/year) spends $96,000. Their FIRE number is $2.4M. A household saving 50% ($60,000/year) spends $60,000. Their FIRE number is $1.5M. They accumulate twice as fast and need $900,000 less. The timeline difference isn’t just 2x. It’s closer to 4x.

FIRE variants: same formula, different targets

The FIRE community uses several variations, all built on the same 4% framework.

Lean FIRE targets $25,000 to $40,000 per year. FIRE number: $625,000 to $1,000,000. Requires frugality, often combined with living in lower cost areas or abroad. Achievable on median income. Less margin for error.

Regular FIRE targets your current lifestyle expenses. The standard 25x calculation. Most calculators default to this.

Fat FIRE targets $100,000 or more per year with a 3.5% withdrawal rate for extra safety. FIRE number: $2.86M at $100,000 per year. Achievable for high earners who save aggressively, but requires a longer runway.

Coast FIRE is the point where you can stop contributing entirely. Your existing savings, compounding to retirement, will grow to your full FIRE number on their own. You still work to cover living expenses but stop accumulating.

Barista FIRE is semi-retirement with part-time work. Your portfolio covers the gap between your expenses and what your job pays. Less required portfolio, more flexibility.

Here’s how the FIRE number scales across common spending levels:

Annual Spending	Lean FIRE	Regular FIRE	Fat FIRE (3.5%)
$30,000	$750,000	$750,000	$857,000
$50,000	N/A	$1,250,000	$1,429,000
$75,000	N/A	$1,875,000	$2,143,000
$100,000	N/A	$2,500,000	$2,857,000
$150,000	N/A	$3,750,000	$4,286,000

Sequence of returns: the main risk

The 4% rule works on average. It can fail badly for retirements starting in a severe bear market.

If your $1.5M portfolio drops 40% in year one to $900,000, and you withdraw $60,000, you have $840,000 left. The portfolio now needs to nearly double just to get back to the original level, and you’re still withdrawing throughout the recovery.

Three strategies that actually help:

Cash buffer. Keep 1 to 2 years of expenses in cash or short bonds. In a crash, draw from cash. Don’t sell equities at the bottom.

Flexible spending. If your $60,000 budget includes $15,000 of discretionary travel and dining, you can cut to $45,000 in bad years. This alone dramatically improves portfolio survival in historical simulations.

Part-time income. Even $15,000 per year from occasional consulting eliminates portfolio withdrawals entirely in down years. This is probably the highest-leverage risk mitigation available.

The sequence risk problem is why your FIRE number is a starting point, not a guarantee. Reaching $1.5M at the beginning of a lost decade is different from reaching it at the beginning of a bull market. The number is the same; the outcome can be completely different.

Healthcare: the FIRE number multiplier

For Americans, healthcare between ages 40 and 65 is the cost that surprises everyone.

An unsubsidized ACA marketplace plan for a 45-year-old costs roughly $400 to $700 per month in premiums. For a couple, that’s $800 to $1,400 per month, which is $10,000 to $17,000 per year, before deductibles and out-of-pocket costs that can hit $15,000 or more in a bad year.

At 4% withdrawal, $25,000 per year in healthcare costs requires $625,000 in additional portfolio. That can add 4 to 6 years to your FIRE timeline.

The workaround: carefully manage your adjusted gross income in early retirement to qualify for ACA subsidies. Income below 400% of the Federal Poverty Level (about $120,000 for a couple in 2025) qualifies for meaningful subsidies. Below 250% FPL, cost-sharing reductions kick in and make Silver plans significantly more affordable.

This requires tax planning, but it’s entirely legal and widely used in the FIRE community. The key is that FIRE retirees in their 40s and 50s often have low ordinary income even with significant wealth, because capital gains and Roth withdrawals can be managed to stay in lower income brackets.

What to actually invest in

The FIRE community has largely converged on a few principles.

Low-cost index funds. Total market or S&P 500 index funds from Vanguard, Fidelity, or Schwab. Expense ratios of 0.03% to 0.05%. The fee difference between a 1% expense ratio fund and a 0.05% fund compounds to hundreds of thousands of dollars over 30 years. At $500,000 invested for 20 years, the difference between 1% and 0.05% in fees is roughly $180,000.

Simple allocation. The three-fund portfolio: US total market, international stocks, US bonds. Adjust the bond percentage based on risk tolerance and how close you are to retirement.

Tax-advantaged accounts first. Max out HSA ($4,300 individual / $8,550 family in 2025), then Roth or traditional IRA ($7,000 / $8,000 if over 50), then 401(k) ($23,500 in 2025), then taxable brokerage.

Roth conversion ladder. If you retire before 59.5, you can’t touch 401(k) funds without a 10% penalty. The conversion ladder works by converting traditional IRA money to Roth in low-income years, then withdrawing those conversions 5 years later. Tax-free. No penalty. This requires planning 5 years before you need the money, which is why starting early matters.

How to use the FIRE number as a milestone system

Treating FIRE as a single binary goal (either you have the number or you don’t) misses a more useful way to think about it. The journey to FIRE has natural milestones worth tracking.

25% of FIRE number: You’ve accumulated 6x annual expenses. Markets now do meaningful work for you. A 7% return on this portfolio adds roughly 1.5x annual expenses per year without contributions.

50% of FIRE number: You’ve reached the halfway point in portfolio terms. Because of compounding, you’re more than halfway to FIRE in time terms. If it took you 10 years to reach 50% of your number, the next 50% typically takes 6 to 8 years, not another 10.

Coast FIRE number: The specific dollar amount where you could stop contributing entirely and still reach full FIRE by retirement age. Calculator shows this automatically. Reaching Coast FIRE is often a more achievable near-term goal than full FIRE.

One year of expenses: $60,000 saved (or whatever your number is). The first year is the hardest psychologically. Once you have one year’s expenses saved and invested, the compounding effect becomes visible.

These milestones matter because they provide motivation checkpoints and also because each one changes your options. Reaching Coast FIRE means career decisions are no longer driven by maximizing income. Reaching 50% means full FIRE is almost certainly achievable barring catastrophic market failure.

Common mistakes in FIRE planning

Underestimating expenses. The most common error. A budget built from memory rather than actual spending is almost always too low. Run your numbers against 12 months of real statements.

Ignoring inflation in the target. If you want $60,000 per year in today’s dollars and you’re 25 years away from retirement, you need a portfolio that generates $125,000 per year in nominal terms (at 3% inflation). Many calculators skip this adjustment.

Assuming constant returns. A spreadsheet that projects 7% every year is mathematically correct on average but misleading for planning. Real markets have years of 25% gains and years of 40% losses. The sequence matters, especially near retirement.

Not accounting for Social Security. Early retirees who stop working at 35 or 40 accumulate fewer Social Security credits. But someone who works until 50 or 55 with a full earnings history has a meaningful Social Security benefit starting at 62. This can reduce the required FIRE portfolio by $250,000 to $600,000 depending on benefit level.

Treating the 4% rule as the floor. The 4% rule is what survives the worst historical scenarios. In most scenarios, you end up with more money than you started with. The median 30-year outcome at 4% from a 60/40 portfolio ends with 2.7 times the starting value. Building a plan around the worst case is conservative, and that’s fine. Just don’t assume you need 3% to be “truly safe.”