FIRE Calculator

FIRE stands for financial independence, retire early: saving and investing enough that your portfolio can pay for your spending indefinitely. This calculator finds your FIRE number from the spending you expect in retirement and a withdrawal rate, then projects your investments month by month to show the age at which you reach it, whether you are on track for your target age, and how much you would need to invest each month to get there.

Everything is in today's dollars. The calculator converts your expected return into a real return after inflation, so the FIRE number does not need to be inflated and the chart reads in today's purchasing power. It also shows your Coast FIRE number, the amount that would grow to your target with no further contributions.

FIRE number = (annual spending − other income) ÷ withdrawal rate

Real return = (1 + nominal return) ÷ (1 + inflation) − 1

Coast number = FIRE number ÷ (1 + real return)^{years to target}

At a 4% withdrawal rate the FIRE number is 25 times annual spending. The time to reach it uses the standard number-of-periods formula with monthly deposits and the monthly equivalent of the real return. With a 7% return and 3% inflation the real return is 3.88%, not 4%, because returns and inflation compound together.

The 4% rule comes from William Bengen's 1994 study of historical US stock and bond returns: withdrawing 4% of the starting balance in the first year and raising it with inflation survived every 30-year period he tested. The 1998 Trinity study reached similar conclusions. Early retirees often plan for 40 or 50 years, and many use 3.25% to 3.5% for a longer horizon. A lower rate means a larger FIRE number but more safety; the table under the result shows the number at five different rates.

Retiring at 50. A 32-year-old with $120,000 invested, adding $2,500 a month and planning to spend $48,000 a year, needs $1,200,000. At a 7% return and 3% inflation the portfolio reaches it at about age 52.7; to retire at exactly 50 they would need to invest $3,104 a month.

Investing $1,000 more. At $3,500 a month the same person reaches financial independence at about 48.7.

Savings rate matters most. Starting from nothing at a 3.88% real return and 4% withdrawals, saving 10% of take-home pay takes 59.3 years, 25% takes 35.5 years, 50% takes 17.6 years and 75% takes 7.2 years. A higher rate both adds to savings and lowers the spending the portfolio must cover.

Spending is the input that moves the result most, since every dollar of annual spending adds 25 dollars to the FIRE number at a 4% rate. Start from what you actually spent over the last twelve months, then remove costs that end at retirement, such as commuting and retirement contributions, and add ones that start, such as private health insurance and travel. If the mortgage will be paid off, leave out its payment but keep property tax and insurance. Variants of FIRE are simply different spending levels: lean FIRE covers a basic budget, fat FIRE a comfortable one.

Real returns arrive unevenly, and a market fall in the first years of retirement does more damage than the same fall later, which a constant-return projection cannot show. Taxes on withdrawals, health insurance before Medicare eligibility at 65, and penalties for early withdrawals from retirement accounts all change the amount you need. Social Security can be entered as other income, but it usually starts later than an early retirement. For a traditional plan around a fixed retirement age, use the retirement savings calculator.