FIRE Calculator: Financial Independence Simulator
See how many years separate you from financial freedom. Enter your savings, contributions and spending — every assumption is yours to change, today or ten years from now
Your Numbers
Assumed to keep pace with inflation, so it stays constant in today's money.
In today's money, including the taxes you expect to pay on withdrawals.
Average yearly growth of your investments before inflation.
Share of the portfolio you withdraw each year. 4% (25× annual spending) is a historical rule of thumb, not a guarantee.
How the FIRE Simulator Works
FIRE stands for Financial Independence, Retire Early. The idea is simple: once your invested portfolio can cover your yearly spending through withdrawals alone, work becomes optional. This simulator divides your yearly spending by your withdrawal rate to find your FIRE number, then adds your contributions and investment growth month by month until your portfolio reaches it.
Everything is in today's money. Instead of asking you to guess future prices, the simulator converts your nominal return into a real (inflation-adjusted) return, so the FIRE number, the chart and your contributions all stay comparable with what you spend today. There is nothing to update over time: change any assumption whenever your life changes and the result recalculates instantly.
Your FIRE Projection
Portfolio Growth (in today's money)
How to use this tool
- Enter your currency symbol, current age and current savings.
- Add your monthly contribution and your expected monthly spending in retirement.
- Set the assumptions: expected annual return, inflation and safe withdrawal rate (4% is the classic starting point).
- Read the FIRE number, the time to reach it, the progress bar and the real return; use “Reset to defaults” to start over.
Worked example
A 30-year-old with 50,000 saved, contributing 2,000 a month and planning to spend 3,000 a month assumes 7% returns, 3% inflation and a 4% withdrawal rate. Annual spending is 36,000, so the FIRE number is 36,000 ÷ 0.04 = 900,000. The real return is (1.07 ÷ 1.03) − 1 ≈ 3.88%, and at that pace the target is reached in about 21 years and 4 months, with current progress at 5.6%. Raising the contribution or lowering spending moves both sides of the equation, which is why both levers matter; the next section compares them with real numbers.
Why this tool exists and where its numbers come from
People planning early retirement need a rough target for the portfolio that could fund their spending. The 4% rule behind it comes from Bengen (1994) and the Trinity Study; both are historical US results, success was high but not guaranteed, and the future may differ.
Sources
- Bengen (1994): Determining Withdrawal Rates Using Historical Data
- Cooley, Hubbard & Walz (1999): Sustainable Withdrawal Rates From Your Retirement Portfolio (follow-up to the 1998 Trinity Study, copy)
For the full method, see the Methodology section just below.
Methodology
The core rule comes from two studies of sustainable portfolio withdrawals: William Bengen's 1994 paper “Determining Withdrawal Rates Using Historical Data” (Journal of Financial Planning) and the 1998 Trinity Study by Cooley, Hubbard and Walz, “Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable” (AAII Journal). Both found that a diversified stock-and-bond portfolio historically sustained an initial withdrawal of about 4% a year, adjusted for inflation, over periods of roughly 30 years — equivalent to a portfolio of 25 times annual spending. Converting your nominal return into a real return uses the Fisher equation: (1 + nominal) ÷ (1 + inflation) − 1. The Trinity paper linked in the sources is the authors' 1999 follow-up, “Sustainable Withdrawal Rates From Your Retirement Portfolio” (Financial Counseling and Planning).
One portfolio, five withdrawal rates, and a 500 decision
Default inputs (savings 50,000, contribution 2,000 a month, spending 3,000 a month, 7% return, 3% inflation, so a real return of 3.88%). Only the withdrawal rate changes:
| Withdrawal rate | FIRE number | Time to independence |
|---|---|---|
| 3% | $1,200,000 | 26 yr 1 mo |
| 3.5% | $1,028,571 | 23 yr 6 mo |
| 4% | $900,000 | 21 yr 4 mo |
| 4.5% | $800,000 | 19 yr 7 mo |
| 5% | $720,000 | 18 yr 1 mo |
How to read it: a more cautious rate raises the target and delays the date, and the effect is not linear. Going from 4% to 3% adds almost five years. The tool does not say which rate is right for you.
A case: Elena, 30, has the default numbers and can free 500 a month. Option one: plan on spending 2,500 in retirement, so the FIRE number falls to 750,000 and the date to 18 yr 8 mo. Option two: contribute 2,500, keep 900,000 as the target and reach it in 18 yr 5 mo. The timing is within three months, but the first plan needs a smaller portfolio and the second relies on keeping a higher savings rate for years. She picks the one she can actually sustain.
Educational projection, not financial advice; taxes, fees and market swings are not modeled.
Books & Tools for Your Path to Financial Independence
Practical picks to help you learn the strategy, track your budget and run the numbers
The Simple Path to Wealth: Your Road Map to Financial Independence and a Rich, Free Life
J L Collins’s book on financial independence through low-cost index funds. One author’s approach, worth reading next to other views; not personal financial advice.
Clever Fox Budget Planner Pro with cash envelopes (black)
An undated hardcover budget planner with cash envelopes and savings and debt trackers, according to the listing.
Texas Instruments BA II Plus Professional financial calculator
A financial calculator with time-value-of-money, cash-flow, NPV and IRR functions, according to the listing, for checking growth scenarios by hand.
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Frequently asked questions
What is my FIRE number and why is it 25 times my spending? ▼
Your FIRE number is the portfolio size at which withdrawing your chosen percentage each year covers your spending. At the classic 4% rate, that is annual spending ÷ 0.04, which equals 25× annual spending. Spending 3,000 a month (36,000 a year) gives a FIRE number of 900,000. Change the withdrawal rate and the multiple changes with it: 3.5% needs about 28.6×.
Is a 4% withdrawal rate safe if I want to retire at 35 or 40? ▼
The studies behind the 4% rule looked at retirements of roughly 30 years. Retiring decades earlier means your money must last 50 years or more, so many researchers suggest starting lower, often around 3% to 3.5%, and staying flexible about spending in bad market years. Nobody can guarantee a safe rate; use this simulator to compare how each rate changes your timeline.
Why does the simulator ask for nominal return and inflation separately? ▼
Because a 7% return with 3% inflation grows your purchasing power by only about 3.9% a year. The simulator combines them into a real return with the Fisher equation and keeps every result in today's money, so your FIRE number is directly comparable with what you spend now. A contribution that rises with inflation stays constant in today's money, which is what the calculator assumes.
Does this include taxes, pensions or healthcare costs? ▼
No. The simulator treats your spending figure as the total amount you need to withdraw. Add the taxes you expect on withdrawals and your healthcare costs to that number. Pensions, Social Security or rental income are not modeled: if you expect them, you can reduce your monthly spending figure by the amount they will cover.