FIRE Calculator estimates the portfolio size and years needed to reach financial independence, based on entered income, expenses, expected return, and withdrawal-rate figures.
FIRE Calculator: Project Your Target Portfolio and Years to Financial Independence
This FIRE Calculator turns Annual Expenses and a Safe Withdrawal Rate into a target portfolio size, then projects how many years of compounding growth and savings it will take to reach it from Current Savings and Annual Income. It is used by people planning early or traditional retirement who want a required-portfolio figure and an estimated timeline rather than a single lump-sum guess.
FIRE Calculator Inputs: Age, Income, Expenses, Return, and Withdrawal Rate
Enter Current Age (years), Current Savings, Annual Income (post-tax), Annual Expenses, Expected ROI (after inflation, annual), and Safe Withdrawal Rate as percentages or currency amounts. The calculator outputs Target FIRE Portfolio, Years to Independence, Wealth Accumulation split, Savings Rate, and Safe Weekly Withdrawal, compounding annually.
How the FIRE Calculator Computes Your Target Portfolio and Years to Reach It
Target FIRE Portfolio divides Annual Expenses by the Safe Withdrawal Rate:
$$\text{Target Portfolio} = \frac{\text{Annual Expenses}}{\text{SWR}}$$
At the default 4% Safe Withdrawal Rate, this is the same as multiplying Annual Expenses by 25 — the “25x expenses” shorthand tied to the 4% rule. The 4% figure is a withdrawal-rate guideline, not a statute or formula, originating from William Bengen’s 1994 research and popularized by the 1998 Trinity Study, which modeled a 30-year retirement horizon; because many FIRE planners retire earlier and need the portfolio to last longer than 30 years, some choose a lower Safe Withdrawal Rate than the historical 4% figure. Annual savings capacity is Annual Income minus Annual Expenses, and Years to Independence solves for $n$ in the standard future value of an ordinary annuity formula:
$$n = \frac{\ln\left(\dfrac{\text{Target} \times r + \text{PMT}}{\text{Current Savings} \times r + \text{PMT}}\right)}{\ln(1 + r)}$$
where $r$ is Expected ROI as a decimal and PMT is the annual savings capacity. A common input mistake is entering a pre-tax income figure in Annual Income (Post-Tax), which overstates PMT and understates the true years to independence.
Current Age, Current Savings, and Annual Income accept non-negative numbers; Annual Expenses and Safe Withdrawal Rate must be entered as positive numbers greater than zero, since both are used as divisors.
If Current Savings already meets or exceeds Target Portfolio, Years to Independence is 0 — the goal is already met. If Expected ROI is entered as 0%, the calculator switches to a straight-line calculation, dividing the remaining portfolio gap directly by annual savings capacity rather than applying the compounding formula above.
If Annual Income does not exceed Annual Expenses, the calculator requires Current Savings to already meet or exceed Target Portfolio before it will compute a result, since a savings capacity of zero or less cannot be projected toward a target through contributions alone.
The resulting timeline is an estimate based on the age, income, expense, return, and withdrawal-rate figures entered — it illustrates a trajectory under constant assumptions rather than a guaranteed retirement date, and it is not personalized investment, tax, or retirement advice, since actual market returns vary year to year and rarely follow one constant annual rate.
Visualizing the Path From Current Savings to Your FIRE Number
FIRE Calculator Questions: Withdrawal Rates, Contributions, and Edge Cases
Where does the 4% Safe Withdrawal Rate default come from?
The 4% figure is a withdrawal-rate guideline from William Bengen’s 1994 research, popularized by the 1998 Trinity Study — not a statute, and not guaranteed for retirement horizons longer than the 30 years the original research modeled.
How does the calculator project years to financial independence?
Income minus Expenses gives annual savings capacity (PMT), compounded once per year at the entered ROI alongside your Current Savings, using the standard future value of an ordinary annuity formula solved for years.
What happens if my expenses are close to or above my income?
If Annual Income does not exceed Annual Expenses, Current Savings must already meet or exceed the Target Portfolio, since the calculator has no positive annual contribution to project growth toward the target.
How does a 0% expected return change the calculation?
With Expected ROI at 0%, Years to Independence is calculated as the remaining portfolio gap divided directly by annual savings capacity, since there is no compounding growth to shorten the timeline.
What does the calculator show if I already have enough saved?
Years to Independence is set to 0, since Current Savings already covers the Target Portfolio calculated from Annual Expenses divided by the Safe Withdrawal Rate — no further accumulation is required.