What is FIRE?

FIRE stands for Financial Independence, Retire Early - a movement focused on aggressive saving and investing during your working years so you can achieve financial independence at a much earlier age than traditional retirement. Adherents aim to accumulate enough invested assets that passive returns can fund their lifestyle indefinitely. Common sub-types include:

LeanFIRE: retiring on a minimal budget (typically under $40k/year in expenses).
FatFIRE: retiring with a higher annual spending target ($80k+ per year) to maintain a comfortable lifestyle.
CoastFIRE: saving enough early that compound growth alone will reach your FIRE number by traditional retirement age, allowing you to “coast” by working just enough to cover current expenses.
BaristaFIRE: semi-retiring into part-time or lower-stress work that covers current expenses while your portfolio continues to grow.

The FIRE number formula

Your FIRE number - the portfolio value needed to retire - comes from the 4% rule, derived from the Trinity Study (Cooley, Hubbard & Walz, 1998) which found that a 4% annual withdrawal from a diversified stock/bond portfolio had a very high survival rate over 30-year periods:

FIRE Number = Annual Expenses × 25

For example, if you spend $50,000/year, your FIRE number is $1,250,000. The progress bar in the calculator above shows your current portfolio as a percentage of this target.

Savings rate and years to FIRE

Your savings rate (what percentage of your income you save and invest) is the single most powerful lever in early retirement. Higher savings rates compress the timeline dramatically:

Savings Rate	Approximate Years to FIRE
10%	~43 years
25%	~32 years
50%	~17 years
65%	~11 years
75%	~7 years
90%	~3 years

(Assumes 5% real portfolio returns and a 25× final multiple. Actual results depend on investment returns, expenses, and taxes.)

Coast FIRE vs. full FIRE

In full FIRE, you stop working entirely and live off portfolio withdrawals. In Coast FIRE, you stop contributing to investments and let compound growth carry your portfolio to your final FIRE number by traditional retirement age. Coast FIRE requires a smaller invested amount but demands that you continue working (at least part-time) to cover living expenses.

Sequence-of-returns risk

The 4% rule’s historical success assumes a diversified portfolio and a 30-year horizon. For longer early retirements (40–60 years), a more conservative withdrawal rate (3.25–3.5%) is often recommended. The greatest risk is a severe market downturn in the first few years of retirement: early losses reduce the portfolio before it can recover, permanently impairing withdrawal capacity.

The Safe Withdrawal Rate debate

The 4% rule originates from research by William Bengen (1994) and was based on 30-year retirement horizons using historical US market data. For early retirees planning for 40\u201360+ year retirements, many researchers and practitioners use a more conservative 3\u20133.5% withdrawal rate. International diversification and a flexible spending strategy (reducing withdrawals during downturns) can support higher withdrawal rates. The "right" withdrawal rate depends on asset allocation, spending flexibility, and time horizon.

Inflation impact

Nominal portfolio growth can be misleading without accounting for inflation. At 2% annual inflation, $60,000/year in today's dollars costs approximately $109,000/year in 30 years. The real (inflation-adjusted) withdrawal rate matters most for long-term planning. A portfolio earning 7% nominally with 2% inflation has a 5% real return \u2014 and your FIRE number should be calculated against your expected real expenses, not nominal ones.