FIRE Number Calculator

Your FIRE number is the portfolio balance at which your investments can fund your lifestyle indefinitely — without a paycheck. Once your portfolio reaches that number, work becomes optional. That’s the core promise of financial independence.

The calculation is straightforward: divide your annual expenses by your safe withdrawal rate.

The logic behind the formula: if your portfolio earns a long-term average return above your withdrawal rate, the principal persists or grows over time. At a 7% average return with a 4% withdrawal, the remaining 3% compounds the portfolio — providing a buffer against bad market years and inflation.

The number feels large at first. For most people with moderate expenses, the target is between $750,000 and $2,500,000. But it’s not a lump sum you produce out of thin air — it’s the product of decades of compounding. The same math that makes the target seem distant is the math that gets you there.

The 4% rule is the most widely cited benchmark in FIRE planning. It originated from the Trinity Study — a 1998 research paper by three professors at Trinity University who analyzed stock and bond portfolio performance over historical market cycles from 1926 to 1995.

Their finding: a portfolio invested 50–75% in stocks, withdrawing 4% of the initial balance annually (adjusted for inflation each year), had a 95%+ historical success rate over 30-year periods. “Success” means the portfolio didn’t run out of money — even through the Great Depression, stagflation of the 1970s, and every other major market downturn in that period.

That 95% figure has made 4% the de facto planning benchmark. It gives you a target (25x annual expenses) that’s both achievable and historically resilient.

The important caveat is timeline. The Trinity Study assumed 30-year retirements. If you retire at 40, you may need your portfolio to last 50–60 years. For longer horizons, most planners recommend a withdrawal rate of 3–3.5% to provide additional margin. A 3% rate means you need 33x annual expenses, but your portfolio’s survival odds over 50+ years are dramatically higher.

The withdrawal rate you choose affects two things simultaneously: how much you need to accumulate, and how long your portfolio will last. A lower withdrawal rate means a larger target but a much more durable portfolio.

There is no universally right answer. Someone retiring at 35 with a 60-year horizon and high flexibility — willing to work part-time in a downturn or reduce spending — can reasonably use 4–5%. Someone retiring at 55 with a conservative allocation and fixed expenses should use 3–3.5%. The calculator above shows all four scenarios side by side so you can see the tradeoffs clearly.

There’s a counterintuitive shift in how you build wealth over time. In the early years, your contributions do the heavy lifting. Your portfolio is relatively small, so even strong market returns produce modest absolute gains. A 7% return on $50,000 is $3,500. Your $18,000 in annual contributions matters far more.

Over time, that relationship inverts. Once your portfolio reaches $500,000, a 7% return produces $35,000 in annual gains — roughly twice what most people contribute. At $1,000,000, that same 7% return adds $70,000 — more than most people’s after-tax salaries. Your portfolio has become its own income engine.

This is why the early years feel painful and slow. Your contributions dominate, and compounding looks nearly flat. But those early contributions are the most valuable ones in the portfolio’s lifetime — they compound the longest. The final dramatic growth you see in a 30-year chart is only possible because of what you invested in year one.

The practical implication: optimize contributions aggressively early. Save every percentage point you can in your 20s and early 30s. Later, focus on staying invested, maintaining your allocation, and not interrupting compounding. Different levers matter at different stages.

FIRE is not a single destination — it’s a spectrum calibrated to how much you spend. Two people with identical incomes and savings rates can have completely different FIRE numbers based on how they plan to live in retirement.

Lean FIRE describes financial independence on a minimal budget — often $25,000–40,000/year, requiring $625,000–$1,000,000 at 4%. This is achievable faster but requires frugality and geographic flexibility (low cost-of-living location, minimal discretionary spending).

Fat FIRE means retiring on a comfortable or generous budget — $80,000–$150,000/year or more, requiring $2,000,000–$3,750,000. This allows for travel, housing upgrades, and a lifestyle similar to peak-earning years.

Coast FIRE is a middle path: reaching the point where you have enough invested that, even with no more contributions, your portfolio will grow to your FIRE number by traditional retirement age. Coast FIRE allows you to stop maximizing savings and work a lower-stress job to cover current expenses.

The right answer depends on what you actually want your life to look like. The most useful thing this calculator can do is show you precisely how changes in annual expenses affect your target and timeline — making the tradeoffs concrete and quantifiable.

Reaching your FIRE number is not the end of the planning problem — it’s the beginning of a different one. The most significant risk in early retirement is sequence of returns: the timing of market downturns matters enormously.

A 30% market crash in year one of retirement is far more damaging than the same crash in year fifteen. Early losses reduce the principal that future gains compound on. A portfolio that loses 30% and then gains 30% is not back to even — it’s 9% below where it started. When you’re withdrawing simultaneously, the damage compounds.

The standard hedges against sequence-of-returns risk: maintain a cash or short-bond buffer (1–3 years of expenses in liquid, low-volatility assets) so you aren’t forced to sell equities in a downturn. Reduce withdrawals in bad years if possible. Keep some income flexibility — a part-time project, consulting, or side income reduces the portfolio withdrawal rate in years when it matters most.

The 4% rule accounts for some of this risk historically, but the Trinity Study assumed reasonably smooth withdrawal behavior. Real early retirees who build flexibility into their withdrawal strategy — spending less when markets are down, more when they’re up — have meaningfully better outcomes than the static rule suggests.