Standard FIRE Calculator

What is Standard FIRE?

FIRE stands for "Financial Independence, Retire Early." Standard FIRE is the canonical version: accumulate a portfolio large enough that, at a safe withdrawal rate, it covers your annual expenses indefinitely. Once you hit it, employment income becomes optional.

The defining number is your FIRE number — the portfolio size that crosses the threshold. At a 4% withdrawal rate, that number is exactly 25× your annual spending. At 3.5%, it's about 28.6×. At 3%, it's 33×. Lower rates buy more safety margin against bad sequences of returns, at the cost of a much larger portfolio.

The math

Standard FIRE math has two pieces. First, the FIRE number:

FIRE Number = Annual Expenses ÷ Safe Withdrawal Rate

A household spending $50,000 per year at a 4% withdrawal rate needs $1,250,000 invested. At 3.5%, the same household needs about $1,428,000.

Second, the time to FIRE: how long current contributions take to reach the target, given an expected real return. For starting balance P, monthly contribution C, monthly real return r, the future value after n months is:

FV(n) = P · (1+r)n + C · ((1+r)n − 1) ÷ r

Solving FV(n) = target gives the number of months until you hit your FIRE number. The calculator above does this in closed form when there are positive contributions and a positive return, and falls back to a simple linear path when the return is zero.

A worked example

Suppose you're 32, spending $48,000/yr in today's dollars, with $80,000 already invested and saving $30,000/yr. You assume 7% real returns and the 4% rule.

• FIRE number: $48,000 ÷ 0.04 = $1,200,000
• Years to FIRE: ~17.5 years
• Age at FIRE: ~49.5
• Projected portfolio at 65 (if you keep contributing): ~$3.7M — well past FIRE

Plug your own numbers in and watch how each lever moves the date. Saving $5k more per year, or trimming $5k off retirement spending, are often worth multiple years of working life.

The biggest reason FIRE plans fail isn't the assumption being wrong; it's nobody remembering which assumption they made.

How to use this calculator

1. Annual expenses — total household spending in today's dollars. Don't inflate it; the model handles inflation through the real-return input.
2. Current invested assets — stocks, index funds, retirement accounts. Exclude home equity and emergency cash.
3. Annual contribution — what you save and invest each year, including employer match. Don't include the principal portion of mortgage payments.
4. Real return — your expected after-inflation return. 7% is a common baseline for diversified equity. Lower it if you hold significant bonds, or if you want a conservative buffer.
5. Withdrawal rate — defaults to 4%. Drop to 3.25–3.5% for very long retirements (40+ years).

What the 4% rule actually says

The "4% rule" is shorthand for findings from the Trinity Study (Cooley, Hubbard, and Walz, 1998) and William Bengen's earlier 1994 paper. They tested historical 30-year retirement windows and found that a portfolio of 50–75% stocks supported a 4% initial withdrawal, adjusted for inflation each year, with very high success rates.

Important caveats:

• 30-year window. If you retire at 40 expecting to live to 90, you're planning for a 50-year window — historically less forgiving.
• U.S. historical bias. The classic studies use U.S. equity returns, which were unusually strong over the 20th century. Globally diversified portfolios show somewhat lower safe rates.
• Sequence risk. Hitting a deep drawdown in the first 5 years of retirement is far worse than hitting one 20 years in. The 4% rule averages this away; reality may not.

For these reasons, many in the FIRE community now target 3.25–3.5% for long retirements, which translates to a 28.6–33× expense multiple. This calculator lets you choose, but the default 4% is fine as a starting point.

Standard FIRE vs Lean FIRE vs Coast FIRE

FIRE comes in flavors. They share the same math but differ in target spending and timing:

• Standard FIRE — typical-middle-class spending ($50–80k/yr), 25× target, retire today.
• Lean FIRE — minimal spending ($25–40k/yr), much smaller portfolio, more frugal lifestyle but reachable years sooner.
• Coast FIRE — the smallest target. Enough invested today that compound growth alone gets you to Standard FIRE by retirement, even if you stop saving.
• Barista FIRE — portfolio plus modest part-time income jointly cover expenses.

What this calculator doesn't model

• Sequence of returns risk. The model uses an average return, which hides the difference between hitting a 30% drawdown year 1 vs year 25.
• Taxes on withdrawals. The 4% rule is typically used pre-tax. If most of your savings are in traditional 401(k), add headroom or lower your withdrawal rate.
• Healthcare costs in early retirement. US healthcare before Medicare is the single biggest variable for early retirees.
• Social Security or pensions. If you expect a meaningful guaranteed income in your 60s, your real FIRE number is lower.
• Lifestyle inflation. The model assumes today's spending equals tomorrow's. In practice, expenses tend to grow with income.