What is a FIRE number?
FIRE stands for Financial Independence, Retire Early. Your FIRE number is the size of the investment portfolio that could cover your spending indefinitely, or at least for a very long retirement, without a paycheck. The usual shortcut divides your annual spending by a safe withdrawal rate:
FIRE number = annual spending ÷ withdrawal rate
At 4%, that is 25 times your annual spending. $40,000 a year needs $1,000,000; $60,000 needs $1,500,000.
Where the 4% rule comes from
Studies of historical US stock and bond returns in the 1990s found that withdrawing 4% of a balanced portfolio in the first year, then raising the amount with inflation, survived every 30-year period tested. Early retirees may need their money to last 40 or 50 years, so many use a more cautious 3.25% to 3.5%. The table shows how your target changes with the rate.
How years to FI are calculated
The calculator grows your current savings at the real return you enter and adds your annual savings at the end of each year, then solves for when the balance reaches your FIRE number:
years = ln((F×r + S) / (B×r + S)) / ln(1 + r)
F is the FIRE number, B your current savings, S your yearly savings and r the real return. Using a real return (after inflation, often 4% to 5% for a stock-heavy portfolio) keeps every number in today's dollars, so you can compare the target directly with your current spending.
Coast FIRE
Coast FIRE is the amount that, left alone with no more contributions, would grow into your full FIRE number by a traditional retirement age. Once you hit it, you only need to earn enough to cover current expenses, which is why some people downshift to part-time or lower-stress work.
Your savings rate is the biggest lever
Spending less helps twice: you save more each year and you need a smaller portfolio. Try lowering your retirement spending by $5,000 and watch both lines move. Remember to plan for health insurance before Medicare age, taxes on withdrawals, and irregular costs such as home repairs and cars when you set your spending number.
Frequently asked questions
How do I calculate my FIRE number?
Divide the amount you expect to spend each year by your withdrawal rate. At 4%, multiply your annual spending by 25: $50,000 a year means a FIRE number of $1,250,000.
Is the 4% rule still safe?
It held up across historical 30-year periods in US markets, but early retirees with longer horizons often use 3.25% to 3.5% for extra safety, and stay flexible with spending in bad markets.
What is lean FIRE and fat FIRE?
Lean FIRE means retiring on a minimal budget with a smaller portfolio; fat FIRE means a comfortable, higher-spending lifestyle and a much bigger target. Enter the spending level you want to see either number.
Should I include my home equity?
Usually not, unless you plan to sell and downsize. The FIRE number should be invested assets that can produce income.