The FIRE number is famously simple: annual spending divided by a withdrawal rate. Spend $60,000 a year and use the 4% rule, and you need $1,500,000. The harder question is the second one — when do I actually get there? That depends on what you have now, what you add each year, and what the market does while you wait. This calculator answers both, using the same year-by-year simulation engine as every other page on this site.
Two honesty notes before you start: the projection uses a constant annual return, so it does not model sequence-of-returns risk (bad early years), and it ignores fund fees and taxes. Both make real outcomes noisier than the line on this page — plan on a range, not a point.
How the math works
Step 1 — the FIRE number. Divide your annual spending by your withdrawal rate. At 4%, you need 25× your annual spending; at 3.5%, about 28.6×; at 5%, 20×. The withdrawal rate is the dial that trades safety against speed.
Step 2 — the timeline. Starting from your current savings, each year the balance grows by your assumed return and then your contribution lands. The simulation repeats until the balance crosses the FIRE number (or hits an 80-year sanity cap, which means the inputs as given never get there — the result card will say so instead of guessing).
FIRE number = annual spending ÷ withdrawal rate
balance[n] = balance[n-1] × (1 + return) + contribution
repeat until balance ≥ FIRE number (cap: 80 years)Watch the third result row: growth. Early on, your contributions do most of the work. By the end, compounding usually does — on the sample below, investment growth contributes more than everything the saver puts in. That crossover, not the FIRE number itself, is the real story of how FIRE happens.
The sample, end to end. You spend $60,000 a year, so at a 4% withdrawal rate your FIRE number is $1,500,000 (25× spending). With $420,000 already saved and $30,000 added each year at an 8% return, you cross it in 12 years with $1,626,945. Of that ending balance, you put in $780,000 (starting balance plus yearly additions) — growth supplied the other $846,945, roughly 78% of the total. Slow at first, then unmistakably compounding.
Terms & definitions
FIRE number
The portfolio size at which you can retire: annual spending divided by your withdrawal rate. At 4%, it is 25× annual spending.
Withdrawal rate
The percentage of your portfolio you withdraw in year one of retirement, then adjust for inflation. 4% is the classic rule of thumb.
Lean FIRE
FIRE achieved by minimizing spending — typically under $40,000 a year — which shrinks the required portfolio proportionally.
Barista FIRE
A stage where investments cover most expenses and a part-time job covers the rest, so no further contributions are needed.
Frequently asked questions
Why does this use a fixed return instead of Monte Carlo simulation?
A fixed rate keeps every number auditable — you can reproduce any result by hand. The trade-off is real: actual markets are volatile, and the order of good and bad years matters (sequence-of-returns risk). That volatility is exactly why the withdrawal rate below carries a safety discount. For probabilistic outcomes, run a dedicated Monte Carlo tool and treat this page as the deterministic backbone.
Why 4%? A guaranteed annuity would pay more than that.
A fair deterministic annuity that matched a 30-year retirement horizon would support a withdrawal rate around 5.16% — meaningfully higher than 4%. The 4% rule is deliberately discounted below that to absorb sequence risk, long retirements, and human behavior. We explain the full reasoning, with the math, in our 4% rule guide. Conservative is the point.
What are Lean FIRE, Barista FIRE, and Coast FIRE?
They are the same math with different dials. Lean FIRE cuts annual spending (often below $40,000), which shrinks the FIRE number fast. Barista FIRE means you have enough invested that a part-time job only needs to cover current expenses — no more contributions. Coast FIRE means your current savings alone will grow to the target with zero further contributions; try the coast FIRE calculator if that’s your situation.
What doesn’t this calculator model?
Fund fees (they silently shrink the return), taxes on contributions and withdrawals, inflation after you retire, pension or Social Security income, and sequence-of-returns risk. Each of these can move your real date by years. This page is the clean deterministic skeleton — layer the rest on before making irreversible decisions.
References
- IRS — Retirement plans and FAQs for individuals: irs.gov/retirement-plans/retirement-plan-faqs
- SSA — Period life table (life expectancy used to frame retirement horizon): ssa.gov/oact/STATS/table4c6.html
- RetirePlot — The 4% rule, with the math: /guides/4-percent-rule/