What is the FIRE number?
FIRE stands for Financial Independence, Retire Early. Your "FIRE number" is a shorthand target that represents the amount of investable assets you need to generate enough income to cover your annual expenses without relying on earned wages. The most common quick rule is the "rule of 25": multiply your expected annual spending by 25 (equivalent to a 4% safe withdrawal rate). This calculator uses your inputs — current savings, monthly contributions, expected return, and a safe withdrawal rate — to estimate that target and how long it might take to reach it.
How this calculator works
The calculator computes a target portfolio size by dividing your annual expenses by the safe withdrawal rate (expressed as a decimal). For example, if you plan to spend $30,000 per year and use a 4% withdrawal rate, your FIRE number would be $30,000 / 0.04 = $750,000 (or 25 × $30,000). Once the target is established, the calculator projects how long it will take to reach that amount based on your current savings, your monthly contribution, and a compound growth assumption for your investments. For simplicity and safety, the projection runs month-by-month and stops when the projected balance meets or exceeds the target or when it reaches a long horizon (100 years) to avoid infinite loops for unrealistic inputs.
Key inputs to consider
- Current savings: All investable balances you plan to use toward retirement (not illiquid assets unless you intend to sell them).
- Estimated annual expenses: The amount you expect to spend each year in early retirement. Be realistic: many lifestyles that work while earning a salary cost less than the lifestyle you maintain once retired, but medical and housing costs can go up.
- Monthly contribution: The amount you can reasonably commit to add to your investments each month. Small increases compound dramatically over time.
- Expected annual return: A long-term, conservative assumption for portfolio growth (many planners use 5–7% for a balanced portfolio; use a lower number for conservative planning).
- Safe withdrawal rate: The percent of your portfolio you plan to withdraw each year in retirement. The classic 4% rule is a guideline, not a guarantee; you can choose a lower rate if you want added safety.
Interpreting the results
Results include your FIRE number, how many months and years it may take to reach that number given your inputs, the projected portfolio balance at that horizon, and the percent of the goal you already have saved. If the projection does not reach the goal within the calculation horizon, the tool returns an indicator showing a long timeframe — this means you may need to save more, assume a higher return (with more risk), reduce expenses, or extend the timeline.
Types of FIRE and practical choices
People pursuing FIRE take different approaches: "Lean FIRE" accepts a minimalist budget and a lower FIRE number; "Fat FIRE" targets a larger nest egg for a more comfortable lifestyle; "Barista FIRE" combines partial work with withdrawals to reduce the target. Your personal choice should match your tolerance for spending flexibility, sequence-of-returns risk, healthcare and insurance needs, and family commitments.
Assumptions and caveats
This calculator makes simplifying assumptions: steady monthly contributions, a fixed long-term return, and a constant withdrawal rate. Real markets fluctuate, taxes and fees matter, and expenses change with age and life events. Use the results as an informed estimate rather than a guaranteed outcome. Consider running multiple scenarios (different return and withdrawal rate assumptions) to understand a realistic range.
Next steps after using the calculator
- Run the calculator with conservative, base, and optimistic assumptions to see a range of outcomes.
- Increase monthly contributions or reduce discretionary spending to close any shortfall faster.
- Consider tax-advantaged accounts and low-cost, diversified funds to improve long-term returns while controlling fees.
- Speak with a financial planner for personalized advice, especially if you have complex taxes, pensions, or health-care considerations.
Use this FIRE calculator as a planning tool to set a concrete savings target and to measure progress. Financial independence is a long-term journey — small consistent decisions compound into meaningful results over time.