How this calculator works
The FIRE number is the simplest formula in personal finance: annual spending ÷ withdrawal rate. Spend $62,000 at a 4% rate and the number is $1.55 million. The time estimate then compounds your current savings and monthly investing at your assumed return until they cross that number — with the honest caveat that a fixed return is a simplification of a bumpy market.
Example calculation
A 35-year-old with $85,000 saved, investing $1,200/month at 7%, targeting $62,000 of spending at 4%: FIRE number $1.55M, reached in about 26 years — around age 61. Raise the monthly investing to $2,000 and it drops to about 21 years.
Common mistakes to avoid
- Using current spending as FIRE spending — many FIRE hopefuls plan leaner post-work budgets, but healthcare premiums are commonly underestimated.
- Forgetting that early retirees face decades of sequence risk — 3.5% is the safer planning rate for 40+ year horizons.
- Ignoring taxes: withdrawals from traditional accounts are income; a Roth conversion ladder between retiring and age 59½ is a standard FIRE tool.
Assumptions and limitations
Constant returns, no market downturns in the crossing decade, no pension or Social Security income, and no taxes on withdrawals. Inflation is deliberately absent from the core number: both your savings and the target are treated in today's dollars. This is an educational estimate, not a promise about your future.
Frequently asked questions
What is the 25x rule and how does it relate to my FIRE number?
The 25x rule is the 4% rule restated: annual spending × 25 equals the portfolio that a 4% withdrawal rate supports (1 ÷ 0.04 = 25). Spend $60,000 and your number is $1.5M. Lean FIRE, regular FIRE, and fat FIRE are just different spending numbers run through the same multiplication — the discipline is in honest spending estimates, not the formula.
How do I calculate my savings rate for FIRE?
Savings rate = (income − spending) ÷ income. A 50% savings rate working from zero typically reaches financial independence in roughly 15–17 years, a 65% rate in about 10.5 years — the relationship is nonlinear because a high savings rate both builds the portfolio faster and lowers the spending your target must cover. This calculator derives your rate automatically from the income and spending inputs.
Does the FIRE number account for inflation?
Both sides are kept in today's dollars: your current savings, your monthly contributions' purchasing power, and the target all speak the same currency. In real planning, contributions usually grow with your income over time; the static contribution here is the main simplification. For the withdrawal phase, see the safe withdrawal rate tool for why the rate itself is the bigger assumption.