How this FIRE calculator works
FIRE stands for Financial Independence, Retire Early. The core idea is simple: once your invested portfolio is large enough that its returns cover your spending, paid work becomes optional. The classic shorthand is the 25x rule — save 25 times your annual expenses and you've reached financial independence.
That 25x figure comes from a 4% safe withdrawal rate. The Trinity study and related research found that a retiree withdrawing about 4% of a diversified stock-and-bond portfolio in year one, then adjusting that amount for inflation, had a high probability of the money lasting 30 years or more. Withdrawing 4% is mathematically identical to needing 25 times your spending; a more cautious 3.5% rate implies roughly 28.5x, while a punchier 5% implies 20x. Slide the safe withdrawal rate above to see how sensitive your target is.
Because retirement can span decades, this tool works in real (after-inflation) returns. Enter a return net of inflation — many people model around 5% for a diversified portfolio — so your FIRE number and the spending it funds are both in today's dollars. We simulate your balance month by month, adding your contribution and growing it at the real rate until it reaches your FIRE number. Read more in our guide to the FIRE movement or the full assumptions on our methodology page. This is education, not financial advice.
Frequently asked questions
- What is a FIRE number?
- It's the size of invested portfolio that can fund your annual spending indefinitely. At a 4% safe withdrawal rate it equals 25× your yearly expenses — so $40,000 of spending implies roughly a $1,000,000 portfolio.
- What is the 4% rule?
- Popularised by the Trinity study, it suggests withdrawing about 4% of your portfolio in the first year of retirement and adjusting for inflation thereafter, with a strong chance the money lasts 30+ years. A 4% rate is the same as a 25× target.
- Does this store my numbers?
- No. Everything runs in your browser. Nothing you type is uploaded or saved on a server.