FIRE calculator
Enter your spending and savings, get your financial independence number and how many years it takes.
Every number is an example, not a forecast or a typical figure. Amounts are in today's dollars; saving is added at the end of each year. 4% comes from 30-year U.S. history.
What is the FI number, and why 25 times your spending?
The financial independence (FI) number is the portfolio that could pay for your spending through withdrawals: yearly spending ÷ withdrawal rate. At a 4% withdrawal rate that is 25 times your yearly spending (1 ÷ 0.04 = 25), at 3.5% it is 28.6 times and at 3% it is 33.3 times. With the example spending of $40,000 a year, the FI number is $1,000,000 at 4%, $1,142,857 at 3.5% and $1,333,333 at 3%, and with $100,000 invested and $30,000 saved each year at a 5% real return you would reach them in 16.9, 18.7 and 20.8 years. All amounts are in today's dollars. The three rates are shown side by side in the “Compare withdrawal rates” view. A lower rate buys more safety margin for a longer retirement, and the spending figure is what you plan to spend after taxes you will owe on withdrawals, not your salary. Michael Kitces has suggested that for early retirees the target should perhaps be a 28-times rule, or 30 times for those who prefer to be a little more conservative, instead of 25.
Where does the 4% rule come from, and does it work for a 40-to-60-year retirement?
It comes from historical U.S. market data over 30-year retirements. William Bengen (Journal of Financial Planning, 1994) tested a 50/50 mix of U.S. stocks and intermediate-term Treasuries from 1926 and found 4% to be the highest first-year withdrawal, raised each year for inflation, that lasted 30 years in every period. In the Trinity study (Cooley, Hubbard and Walz, AAII Journal, February 1998, Table 3), a 4% inflation-adjusted withdrawal lasted through 95% of the 30-year periods from 1926 to 1995 for a 50/50 portfolio, 98% for 75% stocks, 95% for all stocks and only 71% with 25% stocks; at 3% it lasted in every period for all four stock mixes (100%), and at 5% in 76% for the 50/50 mix. Those are 41 overlapping 30-year periods of a single country's history, and the study's payout periods stop at 30 years, so 4% is not validated for 40 to 60 years. Kitces (2012) notes that the baseline research assumed 30 years and reports that Bengen's 1996 work gave 4.1% for 30 years but 3.5% for 45 years, with Blanchett finding 3.5% for 40 years and Pfau 3.3% for 40 years at a 95% confidence level. Those studies point to about 3.3% to 3.5% for 40-year horizons, which is why the calculator shows 3.5% and 3% next to 4%. Test your own plan at more than one rate.
How are the years to financial independence calculated?
The calculator uses a closed form. Starting with savings S, adding A at the end of each year and earning a real return r a year, the balance after t years is S·(1 + r)^t + A·((1 + r)^t − 1) ÷ r. Setting that equal to the FI number and solving gives t = ln((FI + A ÷ r) ÷ (S + A ÷ r)) ÷ ln(1 + r); with r = 0 it is (FI − S) ÷ A. For the example, ($1,000,000 + $600,000) ÷ ($100,000 + $600,000) = 2.2857, and ln of that divided by ln 1.05 is 16.94 years. Because the saving comes at year-end, the table's first year-end balance at or above the target is the end of year 17. A real return means the return after inflation, so every amount stays in today's dollars; to get it, subtract inflation from your nominal return (see the real return calculator). This page compounds once a year, while the retirement calculator compounds monthly and starts from your age, so the same inputs can differ by a fraction of a year.
What is Coast FI?
Coast FI is a term from the financial independence community for the amount that, left alone with no more contributions, grows to your FI number by the age you want to be done: Coast FI number = FI number ÷ (1 + r)^(years until that age). It is simply a present value. In the example the FI number is $1,000,000 and the target age is 55, 20 years away, so you need $376,889 invested today; $100,000 would grow to $265,330, which is $276,889 short of that, so you would still have to save. Once your balance passes the Coast FI number you only have to cover today's expenses until the target age. The calculation depends on the return you assume: at a 3% real return the same plan needs $553,676 today, and at 7% it needs $258,419.
How does the savings rate change the years to FI?
If you start from nothing, the share of your take-home pay that you save decides the time, because it sets both how fast the pile grows and how little you need. With income of 1, saving a share s leaves spending of 1 − s, so the FI number is (1 − s) ÷ withdrawal rate and each year adds s. This is derived from the same formula, not from a study. At a 5% real return and a 4% withdrawal rate it gives 51.4 years at a 10% savings rate, 28.0 at 30%, 16.6 at 50% and 8.8 at 70%. The answer does not depend on the size of your income, only on the share you save. It assumes taxes are already out of the pay you start with, a constant real return, savings added at year-end and spending that stays the same after you stop working; at a 3% return the same savings rates take 69.3, 18.9 and 9.4 years for 10%, 50% and 70%. The “Years by savings rate” view shows the whole table.
How much does the return assumption matter?
A great deal. With the example inputs, a 3% real return gives 20.2 years to the FI number, 5% gives 16.9 and 7% gives 14.7. The page does not know what markets will do: the 5% in the form is an example, not a forecast, and the return is a real one, after inflation. Real returns vary from year to year and can be negative for a long time; the Trinity numbers above come from the history of one country, and the order of returns after you retire can matter as much as the average, because a big loss early in retirement is hard to recover from while you are withdrawing. If you are unsure, enter a low real return and see how many years it adds.
What does the calculator leave out?
Taxes first: withdrawals from traditional retirement accounts are taxed as income, and money taken out of an IRA before age 59½ generally carries a 10% additional tax unless an exception applies, such as a series of substantially equal periodic payments (IRS Topic No. 557). Health insurance before you qualify for Medicare, Social Security and pensions (which the retirement calculator can include), changes in spending over a long retirement, and the cost of raising children are also not modelled. Neither is the order of returns, the main risk behind the “success rate” figures: a steady real return of 5% would let a 4% withdrawal run forever, which the retirement withdrawal calculator will confirm for a fixed return, yet real returns come in sequences. Kitces suggests flexible spending rules to cope, such as guardrails that cut spending after bad years. This is an educational planning estimate, not investment advice.
For planning only — not financial, tax or investment advice; the future can differ from any assumption on this page. Sources, read October 27, 2026: P. L. Cooley, C. M. Hubbard and D. T. Walz, “Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable,” AAII Journal, February 1998, Table 3; W. Bengen, “Determining Withdrawal Rates Using Historical Data,” Journal of Financial Planning 7(4), 1994; M. Kitces, “Adjusting Safe Withdrawal Rates To The Retiree's Time Horizon” (May 1, 2012) and “The Problem With FIREing At 4% And The Need For Flexible Spending Rules” (July 17, 2019); IRS, Topic No. 557, Additional tax on early distributions from traditional and Roth IRAs. Related: the retirement calculator, retirement withdrawal calculator, savings goal calculator, compound interest calculator, 401(k) calculator and real return calculator. How we check our calculators.