FIRE Calculator

What is a FIRE number?

FIRE stands for financial independence, retire early. The idea is simple: once your investments are large enough that a modest yearly withdrawal covers your spending, work becomes optional. That target amount is your FIRE number.

FIRE number = yearly spending ÷ withdrawal rate
At a 4% withdrawal rate: FIRE number = 25 × yearly spending

The calculator then grows what you have invested today, adds your yearly savings, and counts the years until the balance reaches the target:

Balance next year = balance × (1 + real return) + yearly savings

Use a return after inflation (a "real" return) so that the FIRE number and your spending stay in today's dollars.

Where the 4% rule comes from

In 1994 financial planner William Bengen tested withdrawal rates against U.S. market history back to 1926 and found that withdrawing 4% of a stock-and-bond portfolio in the first year, then raising the dollar amount with inflation, had lasted at least 30 years in every historical period he studied. A 1998 study by three Trinity University professors reached a similar conclusion. That is the origin of the "4% rule" and the 25× target.

Two cautions apply to early retirees. First, those studies looked at 30-year retirements; retiring at 40 may mean 50 years or more. Second, the future may not match the past. Many people planning a very early retirement use 3.25–3.5% instead, which raises the target to about 29–31 times spending.

Worked example

A 30-year-old expects to spend $40,000 a year, has $100,000 invested and invests $25,000 a year, assuming a 5% real return.

FIRE number at 4%: 40,000 ÷ 0.04 = $1,000,000.
Still needed: $900,000.
Years to reach it: 19, around age 49.

You can check the years by hand: after n years the balance is 1.05ⁿ × (100,000 + 25,000 ÷ 0.05) − 25,000 ÷ 0.05 = 1.05ⁿ × 600,000 − 500,000. It passes $1,000,000 when 1.05ⁿ ≥ 2.5, which first happens at n = 19.

If spending is $60,000 instead, the target becomes $1,500,000 and the same savings take 25 years. Using a 3.5% withdrawal rate on $60,000 raises the target to about $1,714,286 and the time to 27 years.

Lean, regular and fat FIRE

Lean FIRE: a tight budget, often below the typical household's spending. The calculator shows 75% of your target as a rough lean figure.
Fat FIRE: room for travel, a larger home or helping family. Shown here as 150% of your target.
Coast FIRE: you have saved enough that, with no further contributions, growth alone will reach your target by a normal retirement age, so you only need to earn your current spending.
Barista FIRE: part-time work covers some spending, so the portfolio needs to cover less.

These are informal labels, not standard definitions; use your own numbers.

What speeds up financial independence

The two levers are your savings rate and your spending, and spending counts twice: every $1,000 cut from yearly spending lowers the target by $25,000 at a 4% rate and leaves $1,000 more to invest. Returns matter too, but you control them least. Lowering investment fees adds directly to your return.

Things to plan for

Health insurance before Medicare at 65: include premiums and out-of-pocket costs in your spending.
Taxes on withdrawals: money in traditional 401(k)s and IRAs is taxed when withdrawn; Roth contributions (see the Roth IRA calculator) and taxable accounts behave differently. Spending should include the tax you will owe.
Getting money out before 59½: early withdrawals from retirement accounts usually face a 10% additional tax unless an exception applies, so early retirees often hold a taxable account or plan Roth conversions.
Social Security will usually replace part of your spending later. The Social Security calculator shows how claiming age affects the amount.
Bad early years: a market drop just after you stop working does the most damage. A cash buffer or flexible spending reduces that risk.

The projection assumes a steady return every year, which markets never deliver. Treat the result as a planning estimate, not investment advice, and revisit it as your income and spending change.

Frequently asked questions

How do I calculate my FIRE number?

Divide your expected yearly spending by your withdrawal rate. At 4%, that is 25 times your spending: $40,000 a year needs $1,000,000.

Is the 4% rule safe for early retirement?

It was tested on 30-year retirements using past U.S. market data. For retirements of 40–50 years many planners suggest 3.25–3.5%, which means a target of roughly 29–31 times spending.

How long will it take me to reach FIRE?

It depends mostly on your savings rate. With $100,000 invested, $25,000 saved a year and a 5% real return, a $1,000,000 target takes about 19 years.

Should I use a return before or after inflation?

After inflation. Using a real return of around 4–5% keeps the FIRE number and your spending in today's dollars.

What is Coast FIRE?

The point where your current investments, left to grow with no new contributions, will reach your full target by a traditional retirement age. After that you only need to earn enough to cover current spending.

Sources

William P. Bengen. "Determining Withdrawal Rates Using Historical Data." Journal of Financial Planning, October 1994.
Philip L. Cooley, Carl M. Hubbard and Daniel T. Walz. "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable." AAII Journal, February 1998 (the Trinity study).
Internal Revenue Service. Retirement topics: Exceptions to tax on early distributions.
U.S. Securities and Exchange Commission, Investor.gov. Compound interest calculator.

Last reviewed 2 November 2026. Results are estimates; see our disclaimer.