FIRE Calculator — financial independence number & timeline

How it works

FIRE — Financial Independence, Retire Early — turns on one number: the portfolio big enough that withdrawals cover your spending indefinitely. It is the inverse of your safe withdrawal rate:

FIRE number = annual expenses ÷ withdrawal rate

A 4% withdrawal rate — the figure popularised by the Trinity study of historical retirement outcomes — makes the FIRE number 25 times annual expenses. A more cautious 3.5% rate raises it to about 28.6×; a more aggressive rate lowers it. The rate is yours to set based on your risk tolerance and time horizon.

To estimate when you reach it, the calculator grows your current savings at your expected return and adds each year's contribution, year by year, until the balance hits the FIRE number. Both the return and the withdrawal rate are assumptions, so treat the timeline as a planning guide, not a promise — and remember it ignores taxes and inflation-adjusted spending, which a detailed plan would include.

Worked example

With $40,000 of annual expenses and a 4% withdrawal rate, the FIRE number is 40,000 ÷ 0.04 = $1,000,000 (25× expenses). Starting from $50,000 and adding $20,000 a year at a 7% return, the balance passes $1,000,000 in year 20 — by which point you have invested $450,000 of your own money, with compounding providing the rest.

Frequently asked questions

What is a FIRE number?

It is the amount of invested savings that lets you live off withdrawals. Divide your annual expenses by your safe withdrawal rate: at 4%, that is 25 times your yearly spending.

Why is the FIRE number 25 times expenses?

Because 25 is 1 ÷ 0.04. Withdrawing 4% of a portfolio equal to 25× your expenses gives exactly your annual spending. Choose a different withdrawal rate and the multiple changes: 3.5% is about 28.6×.

What is the 4% rule?

It is a guideline from research on historical retirements suggesting that withdrawing 4% of a portfolio in the first year, then adjusting for inflation, has historically lasted about 30 years. It is a starting point, not a guarantee — many FIRE planners use 3.5% for longer retirements.

How long will it take me to reach FIRE?

It depends on your current savings, how much you add each year, and your return. The calculator grows all three until you hit your FIRE number; a higher savings rate is by far the biggest lever.

Does this account for taxes and inflation?

No — it is a simplified projection. Real plans adjust expenses for inflation, account for taxes on withdrawals, and may use lower return assumptions. Use this to get in the right ballpark.

What is lean FIRE versus fat FIRE?

Lean FIRE targets a modest budget (a smaller FIRE number), while fat FIRE targets a comfortable one (a larger number). Both use the same math — only the annual expenses, and so the target, differ.