FIRE Calculator
Calculate your Financial Independence Retire Early (FIRE) number and projected independence age.
Key concepts
FIRE
Financial Independence, Retire Early — a movement focused on building enough invested assets to cover living expenses without relying on a traditional job.
FIRE number
The portfolio size needed to fund your annual expenses using a safe withdrawal rate, commonly 4% (the "25× rule").
4% rule
A guideline suggesting you can withdraw roughly 4% of your portfolio annually in retirement without depleting it over a ~30-year horizon, based on historical research such as Bengen (1994) and the Trinity Study.
What this tool does
What this tool estimates
Enter your current savings, monthly contributions, expected return, and annual expenses. The calculator projects when your portfolio may reach your FIRE number based on the safe withdrawal rate you choose.
The 4% rule and the 25× shortcut
If you plan to withdraw 4% of your portfolio each year, your FIRE number is roughly annual expenses ÷ 0.04, or about 25× expenses. That rule of thumb comes from historical portfolio research (including William Bengen’s work and the Trinity Study). Longer retirements, different asset mixes, or higher spending volatility may call for a more conservative withdrawal rate — which is why this calculator lets you change the rate.
FIRE number formula
FIRE number = Annual expenses ÷ (Safe withdrawal rate / 100) Example at 4%: FIRE number = Annual expenses × 25
We then project portfolio growth with monthly compounding and monthly contributions until the balance reaches the FIRE number (or until the 60-year projection horizon ends).
Worked example
Suppose annual expenses in retirement are $40,000 and you use a 4% withdrawal rate. Your FIRE number is $40,000 ÷ 0.04 = $1,000,000. If you already have $200,000 invested and contribute regularly, the chart shows when the projected balance may cross $1,000,000 under the return assumption you enter. Change the return and withdrawal rate to stress-test optimistic and conservative cases.
Common mistakes
- Assuming one historical stock-market average will hold for your entire timeline.
- Ignoring taxes, healthcare, and sequence-of-returns risk in early retirement.
- Using a withdrawal rate researched for ~30-year retirements for a much longer FIRE horizon without adjustment.
- Treating the calculator output as a personalized financial plan.
Methodology on this page
FIRE number = expenses ÷ (SWR/100). Portfolio growth uses monthly compounding with end-of-month contributions, consistent with our compound-interest engine. Projections are nominal and educational only.
Read the full FinTools4U methodology →Frequently asked questions
What is the FIRE number?
Your FIRE number is the portfolio size needed to cover annual expenses using a safe withdrawal rate, commonly 4% (about 25× expenses).
Is this financial advice?
No. This tool provides educational projections only and does not account for taxes, inflation, or personal circumstances.
What return rate should I use?
Historical market returns vary substantially depending on the period and asset allocation. Use conservative assumptions and test multiple scenarios — past performance does not guarantee future results.
Sources & methodology references
- William P. Bengen (1994) — Determining Withdrawal Rates Using Historical Data — Foundational research often cited for the ~4% withdrawal guideline.
- Trinity Study (Cooley, Hubbard & Walz) — Historical success rates for withdrawal strategies over multi-decade retirements.
- Investor.gov — Asset Allocation — SEC education on diversification and risk — relevant when choosing return assumptions.