FIRE Calculator – Financial Independence Retire Early | SoCalSolver

The FIRE number is calculated using the inverse of the 4% rule: FIRE Number = Annual Expenses ÷ Safe Withdrawal Rate. For instance, if you plan to spend $40,000 annually in retirement and choose a 3.5% withdrawal rate (conservative for 40–50 year retirements), your FIRE number is $40,000 ÷ 0.035 = $1,142,857. Alternatively, the simpler 25x rule multiplies expenses by 25: $40,000 × 25 = $1,000,000 (equivalent to a 4% withdrawal rate). The choice between 3.5% and 4% depends on your retirement horizon: 4% is historically reasonable for 30 years, while 3.5% is more conservative for 40–50 years. The calculator uses the inverse formula for precision, allowing you to specify custom withdrawal rates.

Time to FIRE is calculated via compound interest with regular contributions: FV = PV × (1+r)^t + PMT × [((1+r)^t – 1) ÷ r], where PV is current savings, PMT is annual contributions, r is real return (nominal return minus inflation), and t is years. Example: $50,000 current savings, $25,000 annual contributions, 4.5% real return (7% nominal minus 2.5% inflation), over 20 years yields approximately $1,440,000. If your FIRE number is $1,000,000, you've exceeded the target. This formula is critical because it accounts for both the time value of money and the compounding effect of regular savings.

Savings rate is paramount: it's the percentage of income saved. The research strongly correlates savings rate to years to FIRE—25% savings rate requires ~32 years; 50% requires ~17 years; 70% requires ~7 years. Savings rate = (Annual Income – Annual Expenses) ÷ Annual Income × 100. Increasing savings rate is more powerful than chasing higher returns because you control savings directly, while returns are market-dependent.

Inflation erodes both purchasing power and real returns. If you plan to spend $40,000 today and inflation is 2.5%, you'll need $40,000 × 1.025^20 = $65,000 in 20 years. Similarly, nominal returns of 7% become real returns of 7% – 2.5% = 4.5% after inflation. The calculator uses real returns (post-inflation) for accurate projections. Coast FIRE is calculated as: Capital Needed Now = FIRE Number ÷ (1+r)^(Years until target). Barista FIRE reduces the FIRE number by subtracting part-time income.

Success probability is estimated by comparing your projected portfolio to your FIRE number. If projected portfolio exceeds FIRE number by 20%+ at your target age, success probability is ~85% (accounts for market volatility). If it meets the target, ~75%. If it falls short, ~60%. This is a simplified heuristic; rigorous approaches use Monte Carlo simulation or historical backtesting (see References). Aim to be conservative when planning multi-decade retirements and consider sequence-of-returns risk mitigation.

Comprehensive FIRE calculator for financial independence and early retirement planning, supporting five FIRE variants: Lean, Regular, Fat, Coast, and Barista FIRE.

Automatic calculation of FIRE Number (required capital), savings rate, years to financial independence, and portfolio projections using compound interest formulas with real-return inputs.

Accounts for multiple withdrawal rate options (4%, 3.5%, 3%) and long retirement horizons (30–50 years).

Coast FIRE and Barista FIRE with specific calculations: Coast reduces required capital now via longer growth period; Barista reduces FIRE number by part-time income.

Success probability estimates (60–85%) based on projected portfolio versus FIRE number surplus/shortfall, provided as a heuristic. Users are encouraged to run Monte Carlo or backtesting analyses for rigorous assessment.

Detailed documentation, author credentials, references, and privacy notice included to improve transparency and trustworthiness.