Calculate Your FIRE Number
Key Takeaways
- ▸Your FIRE number is 25× your annual expenses — the portfolio size that funds your retirement.
- ▸The 4% safe withdrawal rate is the foundation: withdraw 4% per year and your money lasts 30+ years.
- ▸Inflation erodes purchasing power — factor in a 2–3% annual inflation rate in every projection.
- ▸Time in the market matters more than timing — starting earlier dramatically shortens the path to FIRE.
Financial Independence, Retire Early (FIRE) is a movement built on a simple mathematical principle: if your investment portfolio generates enough passive income to cover your living expenses, you no longer need to trade your time for money. The FIRE Calculator helps you discover exactly how far you are from that point.
Whether you are pursuing lean FIRE on a frugal budget, fat FIRE with a comfortable lifestyle, or barista FIRE with part-time income, the core math is the same. Enter your current savings, monthly contribution, expected return, and annual expenses to see your projected timeline.
What Is the FIRE Number?
The FIRE number is the total investment portfolio size you need to retire. It is calculated by multiplying your annual expenses by 25 — a figure derived from the famous Trinity Study, which found that a 4% annual withdrawal from a diversified portfolio has historically survived 30-year retirement periods in nearly all market conditions. For example, if you spend €30,000 per year, your FIRE number is €750,000. Reduce your expenses and the target shrinks; increase your lifestyle and the target grows. This simple multiplier is the most powerful lever in FIRE planning.
Is the 4% Rule Still Valid?
The 4% safe withdrawal rate (SWR) originates from a 1994 study by William Bengen and was later confirmed by the Trinity Study. It assumes a 50/50 stocks-bonds portfolio, a 30-year retirement horizon, and US historical market returns. Critics argue that lower current bond yields, higher valuations, and longer retirements (40–50 years for early retirees) make 3–3.5% a safer target. European investors should also consider that European market returns have historically been slightly lower than US returns. The calculator lets you adjust the withdrawal rate so you can stress-test your plan.
FIRE Calculator
Financial Independence, Retire Early
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Try DonkyCapital FreeHow Time and Inflation Shape Your Path
Compound growth is your greatest ally on the road to FIRE — but inflation is the silent enemy. A portfolio growing at 7% per year in nominal terms grows at roughly 4–5% in real terms after a 2–3% inflation assumption. This means your FIRE number in future euros is higher than today's equivalent. The calculator applies real return rates so the projected portfolio value is expressed in today's purchasing power. Starting ten years earlier can cut the required savings rate nearly in half, because compounding has more time to do the heavy lifting. Every year of delay has an exponential, not linear, cost.
Frequently Asked Questions
What is FIRE and who is it for?
FIRE stands for Financial Independence, Retire Early. It is a personal finance strategy aimed at saving and investing aggressively — typically 40–70% of income — to reach a point where investment returns cover all living expenses. It is not exclusively for high earners; the key variable is the gap between income and expenses, not income alone.
How do I calculate my FIRE number?
Multiply your planned annual retirement expenses by 25. This gives you the portfolio size needed to sustain a 4% annual withdrawal indefinitely. For example, annual expenses of €40,000 × 25 = a FIRE number of €1,000,000. Use the calculator to refine this with your current savings, monthly contributions, and expected investment returns.
What is the difference between lean FIRE and fat FIRE?
Lean FIRE means retiring on a minimalist budget — typically under €25,000 per year — which requires a smaller portfolio but demands strict spending discipline. Fat FIRE targets a comfortable or even luxurious lifestyle, often above €80,000 per year, requiring a much larger portfolio. Barista FIRE is a middle path where part-time work covers some expenses, reducing the portfolio requirement.
Is a 4% withdrawal rate safe for European investors?
The 4% rule was derived from US market data. European investors face historically lower equity returns and different sequence-of-returns risk. Many European FIRE practitioners use 3–3.5% as a more conservative target, especially for very long retirement horizons of 40+ years. The calculator lets you customize the withdrawal rate to suit your risk tolerance.
How can I track my progress toward FIRE?
Tracking your net worth, savings rate, and investment portfolio consistently is essential. DonkyCapital connects to your brokers and bank accounts to give you a single, real-time view of your entire portfolio — making it easy to measure how close you are to your FIRE number every month.
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