$500 a month for 15 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $122,329 | $32,329 | $78,518 |
| 5% | $132,412 | $42,412 | $84,990 |
| 6% | $143,456 | $53,456 | $92,079 |
| 7% | $155,552 | $65,552 | $99,843 |
| 8% | $168,803 | $78,803 | $108,348 |
| 10% | $199,222 | $109,222 | $127,873 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $6,000 | $6,190 | $6,010 |
| 2 | $12,000 | $12,814 | $12,078 |
| 3 | $18,000 | $19,901 | $18,212 |
| 4 | $24,000 | $27,484 | $24,419 |
| 5 | $30,000 | $35,598 | $30,707 |
| 6 | $36,000 | $44,280 | $37,084 |
| 7 | $42,000 | $53,570 | $43,557 |
| 8 | $48,000 | $63,510 | $50,135 |
| 9 | $54,000 | $74,146 | $56,826 |
| 10 | $60,000 | $85,526 | $63,639 |
| 11 | $66,000 | $97,703 | $70,583 |
| 12 | $72,000 | $110,732 | $77,665 |
| 13 | $78,000 | $124,674 | $84,897 |
| 14 | $84,000 | $139,591 | $92,286 |
| 15 | $90,000 | $155,552 | $99,843 |
The range in 1,000 simulated markets
A 7% average does not arrive as 7% every year. In 1,000 simulated sequences of returns averaging 7% with 12% volatility, this is where $500 a month ended up: 1 in 10 markets finished below the first figure, half below the middle one, and 1 in 10 above the last.
| After | Weak (1 in 10 lower) | Middle | Strong (1 in 10 higher) |
|---|---|---|---|
| 8 years | $48,666 | $62,518 | $78,848 |
| 15 years | $103,320 | $148,640 | $211,346 |
The middle of the simulation sits below the steady 7% figure of $155,552 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $155,552 would pay in retirement
At a 4% first-year withdrawal, $155,552 pays about $6,222 a year, $519 a month, before tax; in today’s dollars that is about $3,994 a year. How long a balance near it lasts at each withdrawal: how long $150,000 lasts. To stop saving early and let growth do the rest, see Coast FIRE numbers by age.
$6,000 a year fits in an IRA, whose 2026 limit is $7,500 under 50. See contribution limits, the 401(k) calculator and the Roth IRA calculator.
$500 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| $500 a month for 5 years | $35,598 | $30,707 |
| $500 a month for 10 years | $85,526 | $63,639 |
| 15 years | $155,552 | $99,843 |
| $500 a month for 20 years | $253,768 | $140,505 |
| $500 a month for 25 years | $391,521 | $186,993 |
| $500 a month for 30 years | $584,726 | $240,899 |
| $500 a month for 35 years | $855,707 | $304,104 |
| $500 a month for 40 years | $1,235,771 | $378,834 |
Other amounts for 15 years
$50 a month: $15,555, $100 a month: $31,110, $150 a month: $46,666, $200 a month: $62,221, $250 a month: $77,776, $300 a month: $93,331, $400 a month: $124,442, $600 a month: $186,663, $750 a month: $233,329, $1,000 a month: $311,105, $1,500 a month: $466,657, $2,000 a month: $622,210, $2,500 a month: $777,762, $3,000 a month: $933,314, $5,000 a month: $1,555,524.
How it is worked out
Monthly amounts are deposited at the end of each month and compounded monthly at the rate that equals the annual return; lump sums compound once a year. The headline return is 7% a year, the Trinity-style average the site’s retirement pages use; stock-heavy portfolios have averaged more over long periods and bond-heavy ones less, which is why every page shows 4% to 10%. Today’s dollars divide by 3% inflation a year. The range comes from 1,000 simulated sequences of yearly returns averaging 7% with 12% volatility, with each year’s deposits added through the year. Fees and taxes are not taken out. More on the methodology page.