Financial Independence (FIRE) Calculator
How many years until you reach financial independence?
Enter your planned annual expenses in retirement, your safe withdrawal rate, current savings, monthly contribution, and expected return. The calculator shows your FIRE number, the gap remaining, and how many years until you reach financial independence.
FIRE — financial independence and early retirement explained
FIRE stands for Financial Independence, Retire Early. It is a financial planning framework built around a simple goal: accumulate enough invested assets that the returns from those investments cover your living expenses indefinitely, making employment optional. The movement gained mainstream attention in the 2010s through the writing of bloggers and authors like Mr Money Mustache and the work of JL Collins, though the core mathematics have been understood for decades.
The foundation of FIRE planning is the FIRE number — the total invested portfolio value at which you can retire sustainably. This is calculated by dividing annual expenses by the safe withdrawal rate (usually expressed as a percentage). At a 4% withdrawal rate, the FIRE number is 25 times annual expenses. At a 3.5% rate, it is approximately 28.6 times annual expenses. The withdrawal rate you choose reflects how conservative you want to be about portfolio longevity.
The 4% rule and its origins
The 4% safe withdrawal rate comes from the Trinity Study, a 1998 academic paper by professors at Trinity University that analysed historical portfolio returns and calculated what withdrawal rate a retiree could sustain over a 30-year retirement period without running out of money. Using a 50/50 stock-bond portfolio, the study found that a 4% annual withdrawal rate had a historically high success rate over 30-year periods. The FIRE community adopted this as a planning benchmark, though practitioners often use slightly more conservative rates of 3–3.5% for very long retirements (40–50 years).
It is important to understand what the 4% rule is and is not. It is a historical observation about what has worked in past market conditions, not a guarantee of future portfolio survival. It assumes a diversified portfolio invested in equities and bonds, annual rebalancing, and withdrawals adjusted for inflation. It does not account for sequence of returns risk (retiring into a market downturn), changes in spending, or significant one-off expenses. Most FIRE practitioners treat it as a planning guideline and build in additional margins of safety through flexible spending, part-time work, or lower withdrawal rates.
Savings rate is the primary driver of time to FIRE
The most important variable in FIRE planning is not investment return — it is savings rate. The percentage of income you save and invest each month is the dominant factor determining how quickly you accumulate wealth. Mathematical analysis shows that at a 10% savings rate, reaching financial independence takes approximately 40 years. At a 25% savings rate, it takes about 31 years. At a 50% savings rate, around 17 years. At a 75% savings rate, approximately 7 years. These figures assume investment returns roughly matching inflation-adjusted historical averages.
This analysis explains why the FIRE community tends to emphasise spending reduction at least as much as income growth. A person earning a high salary who spends 95% of it is in approximately the same FIRE timeline as a person earning a modest salary who also saves 5%. The absolute income level matters primarily as a ceiling on possible savings; the savings rate is what drives the trajectory.
Types of FIRE
The FIRE framework has several variations tailored to different lifestyles and risk tolerances. Lean FIRE targets a minimal lifestyle in retirement with low annual expenses and a correspondingly lower FIRE number. Fat FIRE targets a comfortable or wealthy lifestyle in retirement, requiring a larger portfolio. Barista FIRE — a middle path — involves reaching a portfolio size that covers most expenses while maintaining a part-time income (often from a low-stress job) to cover the remainder and preserve the portfolio. Coast FIRE refers to the point at which your existing portfolio, even without further contributions, will grow to the full FIRE number by traditional retirement age through compound returns alone.
How this calculator works
The calculator computes your FIRE number from annual expenses and withdrawal rate. It then determines years to FIRE by solving for the time at which your savings, growing at the specified investment return with monthly contributions added, reaches the FIRE target. The formula accounts for compound growth on existing savings and the future value of monthly contributions simultaneously. The result is a projection, not a guarantee — actual timing depends on real investment returns, which will vary year to year.
