Retirement
FIRE Number Calculator
Calculate your FIRE number — the portfolio size that lets you retire on investment returns — and how many years until you reach it. Enter your annual expenses, savings rate, and expected returns.
Retirement
FIRE Number Calculator
Result
FIRE — Financial Independence, Retire Early — is the idea that if you save aggressively enough during your working years, your investment portfolio can eventually cover your living expenses indefinitely, freeing you from needing a paycheck. The math is well-established and surprisingly simple: there's a specific portfolio size that makes you financially independent, and a specific timeline depending on how much you save. This calculator does both.
How this calculator works
You enter:
- Annual expenses you expect in early retirement.
- Current investments, what you already have saved.
- Annual savings, what you can add to investments each year.
- Expected annual return, usually 5-7% real (i.e., after inflation) for a diversified portfolio.
The calculator does two things: it computes your FIRE number using the 4% rule (25× annual expenses), and it projects how many years until your current savings + future contributions + compounded growth reach that target.
The 4% rule, explained
The foundation of FIRE math is the 4% rule, drawn from the Trinity Study and subsequent research. The rule says: if you withdraw 4% of your starting portfolio in year one of retirement, adjust that dollar amount for inflation each year after, your portfolio is very likely to last at least 30 years.
If you need $40,000/year to live on, your FIRE number is $40,000 ÷ 0.04 = $1,000,000. If you need $80,000, your FIRE number is $2,000,000. The multiplier (25×) and the withdrawal rate (4%) are two sides of the same equation.
The 4% rule has held up across most historical 30-year periods including the Great Depression, the 1970s stagflation, and the 2000s lost decade. It's not a guarantee — particularly for very long retirements (40-50 years) — but it's the most widely accepted starting point for FIRE planning.
The four FIRE flavors
FIRE has split into variants targeting different lifestyles:
- Lean FIRE. Annual expenses under $40,000. Smaller portfolio needed ($1M or less), faster to reach, but requires a minimalist lifestyle indefinitely.
- Regular FIRE. Annual expenses $40,000-$100,000. Portfolio target $1M-$2.5M. The original mainstream FIRE target.
- Fat FIRE. Annual expenses above $100,000. Portfolio target $2.5M+. Maintains a fully comfortable lifestyle but takes longer to reach.
- Coast FIRE. You've saved enough that compound growth alone, without further contributions, will reach a normal-retirement target. You can stop saving aggressively and "coast" — work just enough to cover current expenses.
Savings rate is the single most important variable
The Mr. Money Mustache framework popularized a counterintuitive truth: how much you save (as a percentage of after-tax income) matters more than how much you earn, more than how aggressive your investments are, and more than tax optimization. Here's the approximate math:
10% savings rate: ~51 years
20% savings rate: ~37 years
30% savings rate: ~28 years
50% savings rate: ~17 years
70% savings rate: ~9 years
The reason: when you save 50% of your income, you're simultaneously building wealth twice as fast and lowering the amount of wealth you'll eventually need (because the lower spending becomes your retirement standard). Both effects compound.
Sequence of returns risk — the FIRE-specific danger
The 4% rule's biggest weakness is what happens if you retire right before a major market crash. A 40% portfolio drop in your first year of retirement, combined with withdrawals, can permanently damage your portfolio in ways that don't recover. The same drop in year 10 of retirement is much less damaging because your portfolio has had time to grow first.
Common mitigations: keep 1-3 years of expenses in cash or bonds (the "bucket strategy") so you can avoid selling stocks in a downturn; be flexible with spending in bad years; or aim for a slightly lower withdrawal rate (3.0-3.5%) to add buffer.
Variables outside the calculation
FIRE projections are inherently long-range and include simplifying assumptions:
- Healthcare in early retirement is a major cost wildcard. Pre-Medicare retirees often pay $1,000-$2,000/month for ACA marketplace plans, depending on income and state. Subsidies can dramatically reduce this for lower retirement incomes.
- Social Security is not factored in here. Most FIRE planners treat it as a backstop rather than a foundation, since starting it before full retirement age cuts the benefit by 25-30%.
- Taxes in retirement depend on the account mix (taxable, traditional, Roth) and your withdrawal strategy. Withdrawing from a taxable account is usually most tax-efficient first, then traditional, then Roth.
- Lifestyle inflation after retirement isn't modeled. If your spending creeps up by even 1% real per year over 30 years, your FIRE number is off by a meaningful amount.
The calculator is a planning tool, not a guarantee. Most FIRE practitioners run the math, then re-run it every few years as their savings, returns, and life plans evolve.
Common questions
What is my FIRE number?
Your FIRE number is 25 times your expected annual expenses in retirement — the portfolio size that, using the 4% withdrawal rule, should sustain those expenses indefinitely. If you need $50,000/year, your FIRE number is $1.25M. If you need $80,000/year, it's $2M. Use the calculator above to compute yours.
Is the 4% rule still valid in 2026?
Yes, with caveats. The 4% rule has held up across most historical 30-year periods, including major downturns. For very long retirements (40-50 years, common in early-FIRE scenarios), some researchers suggest using 3.0-3.5% instead. The rule is a strong starting point but not a guarantee — flexibility in spending during down years adds significant safety.
What's the difference between Lean, Fat, and Coast FIRE?
Lean FIRE: under $40,000/year in expenses, requires under $1M portfolio. Fat FIRE: $100,000+/year expenses, requires $2.5M+ portfolio. Coast FIRE: you've saved enough that compound growth alone (without further contributions) will reach a normal retirement target — so you can stop saving aggressively and just cover current expenses with lighter work.
How do I handle healthcare in early retirement?
Healthcare is the largest financial wildcard in pre-Medicare FIRE. Options: ACA marketplace plans (subsidies can lower costs significantly if your taxable retirement income is modest); spouse's employer plan if applicable; healthcare-focused HSAs built during working years; or geographic arbitrage to lower-cost states or countries. Budget conservatively — $1,000-$1,500/month per person is realistic in many states.
What's sequence of returns risk?
The risk that a major market downturn in the first few years of retirement permanently damages your portfolio, because you're withdrawing from a smaller base before recovery. The same loss later in retirement is much less harmful. Common mitigations: hold 1-3 years of expenses in cash/bonds, be willing to cut spending in bad years, or use a slightly lower withdrawal rate as a buffer.
Should I include Social Security in my FIRE calculations?
Most FIRE planners treat Social Security as a backstop, not a foundation. If you retire at 45, Social Security is 20-25 years away and benefits could change. Run your FIRE math as if Social Security doesn't exist; when it does kick in (typically at 62-70), it becomes welcome additional income rather than something you depended on.
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A note on this estimate
WalletCalcs provides educational estimates only. Results are not financial, tax, lending, legal, or investment advice. Always confirm important decisions with the appropriate professional or provider.