FIRE & Compound Interest Calculator
Project your path to financial independence: monthly contributions, compound growth, inflation-adjusted purchasing power, the 4% rule and the exact age your portfolio covers your expenses.
Your assumptions
Results
FIRE number
$900,000
Annual spending ÷ withdrawal rate, in today's money.
Financially independent at
61 yrs
Time to independence: 29 years
Portfolio at target age
$893,870
In today's money: $573,119
Investment growth
$2,030,794
82% of the final portfolio comes from compounding
Total contributed
$435,422
Sustainable annual income
$22,925
Monthly saving needed to hit the target on time
$2,933
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Portfolio projection
Year by year
| Age | Balance | Real value | Contributed | Growth |
|---|---|---|---|---|
| 33 | $72,070 | $70,313 | $68,000 | $4,070 |
| 34 | $96,057 | $91,429 | $86,360 | $9,697 |
| 35 | $122,102 | $113,384 | $105,087 | $17,015 |
| 36 | $150,356 | $136,215 | $124,189 | $26,167 |
| 37 | $180,982 | $159,962 | $143,673 | $37,310 |
| 38 | $214,154 | $184,665 | $163,546 | $50,608 |
| 39 | $250,059 | $210,366 | $183,817 | $66,241 |
| 40 | $288,894 | $237,109 | $204,493 | $84,401 |
| 41 | $330,875 | $264,941 | $225,583 | $105,292 |
| 42 | $376,230 | $293,910 | $247,095 | $129,135 |
| 43 | $425,203 | $324,066 | $269,037 | $156,166 |
| 44 | $478,057 | $355,462 | $291,418 | $186,640 |
| 45 | $535,073 | $388,153 | $314,246 | $220,827 |
| 46 | $596,551 | $422,195 | $337,531 | $259,020 |
| 47 | $662,813 | $457,650 | $361,282 | $301,531 |
| 48 | $734,203 | $494,578 | $385,507 | $348,696 |
| 49 | $811,091 | $533,045 | $410,217 | $400,873 |
| 50 | $893,870 | $573,119 | $435,422 | $458,449 |
| 51 | $956,441 | $598,280 | $435,422 | $521,019 |
| 52 | $1,023,392 | $624,546 | $435,422 | $587,970 |
| 53 | $1,095,029 | $651,966 | $435,422 | $659,608 |
| 54 | $1,171,682 | $680,588 | $435,422 | $736,260 |
| 55 | $1,253,699 | $710,468 | $435,422 | $818,278 |
| 56 | $1,341,458 | $741,659 | $435,422 | $906,037 |
| 57 | $1,435,360 | $774,220 | $435,422 | $999,939 |
| 58 | $1,535,835 | $808,210 | $435,422 | $1,100,414 |
| 59 | $1,643,344 | $843,692 | $435,422 | $1,207,922 |
| 60 | $1,758,378 | $880,732 | $435,422 | $1,322,956 |
| 61 | $1,881,464 | $919,399 | $435,422 | $1,446,043 |
| 62 | $2,013,167 | $959,763 | $435,422 | $1,577,745 |
| 63 | $2,154,089 | $1,001,899 | $435,422 | $1,718,667 |
| 64 | $2,304,875 | $1,045,884 | $435,422 | $1,869,453 |
| 65 | $2,466,216 | $1,091,801 | $435,422 | $2,030,794 |
Features
- Monthly compounding with annual contribution growth
- Inflation-adjusted (real) purchasing power line
- FIRE number from any safe withdrawal rate
- Interactive contribution slider
- Year-by-year growth chart and data table
Frequently asked questions
How the maths works
The projection compounds monthly and separates nominal currency from real purchasing power, because a portfolio that doubles while prices double has not made you richer.
- 1Convert the annual return r into a monthly rate: rm = (1 + r)^(1/12) − 1.
- 2For every month: balance = balance × (1 + rm) + contribution.
- 3Increase the contribution once per year by the salary-growth rate.
- 4Deflate the balance to today's money: real = nominal ÷ (1 + i)^years, where i is inflation.
- 5FIRE number = annual spending ÷ safe withdrawal rate (4% → 25× spending).
- 6Inflate the target forward each year and report the first year the nominal balance clears it.
Returns are modelled as a smooth average. Real markets are volatile and sequence-of-returns risk matters in the first years of withdrawal — treat the output as a planning baseline, not a promise.
Everything you need to know
Why compounding beats contribution size over time
In the first years, almost all portfolio growth comes from the money you deposit. Somewhere between year ten and year fifteen — depending on the return you assume — the annual gain produced by the portfolio itself overtakes the annual contribution. From that point on, time in the market matters more than the size of each deposit.
This is why the chart shows contributions and total balance separately: the gap between the two lines is the part of your wealth that compounding built for you.
Reading the 4% rule correctly
The 4% safe withdrawal rate comes from the Trinity study and its successors, which tested historical 30-year retirements against a portfolio of stocks and bonds. It implies a FIRE number of roughly 25 times annual spending.
It is a heuristic, not a law. Longer retirements, lower expected returns, high fees or an early bear market all argue for a lower rate — 3.25% to 3.5% is a common conservative choice, which raises the target to roughly 29–31 times spending.
- 4.0% → 25× annual spending
- 3.5% → about 29× annual spending
- 3.0% → about 33× annual spending
- 5.0% → 20× annual spending, but with materially higher depletion risk
Inflation is the quiet variable
At 2.5% inflation, prices roughly double in 28 years. A portfolio target set in today's money must therefore be inflated to the year you actually retire, otherwise you will hit a nominal number that no longer buys the life you planned.
The calculator does both: the nominal line shows the balance you will literally see in your account, and the real line shows what it is worth in the prices you know today.
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FIRE scenarios
Pre-filled starting points for common Financial Independence goals.
Fat FIRE for a Tech Engineer
A senior tech professional who wants a comfortable, premium retirement rather than a lean one.
Lean FIRE for a Digital Nomad
A location-independent worker who keeps expenses low so the target portfolio stays small.
Barista FIRE — Semi-Retired
Someone who reduces hours instead of stopping completely, so the portfolio only covers the gap.
Coast FIRE in Your 20s
A young saver who front-loads contributions and then coasts on market growth.