$600 a month for 15 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $146,794 | $38,794 | $94,222 |
| 5% | $158,895 | $50,895 | $101,988 |
| 6% | $172,147 | $64,147 | $110,495 |
| 7% | $186,663 | $78,663 | $119,812 |
| 8% | $202,564 | $94,564 | $130,018 |
| 10% | $239,066 | $131,066 | $153,448 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $7,200 | $7,428 | $7,212 |
| 2 | $14,400 | $15,376 | $14,494 |
| 3 | $21,600 | $23,881 | $21,854 |
| 4 | $28,800 | $32,981 | $29,303 |
| 5 | $36,000 | $42,718 | $36,849 |
| 6 | $43,200 | $53,136 | $44,500 |
| 7 | $50,400 | $64,284 | $52,268 |
| 8 | $57,600 | $76,212 | $60,162 |
| 9 | $64,800 | $88,975 | $68,192 |
| 10 | $72,000 | $102,631 | $76,367 |
| 11 | $79,200 | $117,243 | $84,699 |
| 12 | $86,400 | $132,879 | $93,198 |
| 13 | $93,600 | $149,608 | $101,876 |
| 14 | $100,800 | $167,509 | $110,743 |
| 15 | $108,000 | $186,663 | $119,812 |
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 $600 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 | $58,399 | $75,021 | $94,617 |
| 15 years | $123,983 | $178,368 | $253,615 |
The middle of the simulation sits below the steady 7% figure of $186,663 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $186,663 would pay in retirement
At a 4% first-year withdrawal, $186,663 pays about $7,467 a year, $622 a month, before tax; in today’s dollars that is about $4,792 a year. How long a balance near it lasts at each withdrawal: how long $200,000 lasts. To stop saving early and let growth do the rest, see Coast FIRE numbers by age.
$7,200 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.
$600 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| $600 a month for 5 years | $42,718 | $36,849 |
| $600 a month for 10 years | $102,631 | $76,367 |
| 15 years | $186,663 | $119,812 |
| $600 a month for 20 years | $304,522 | $168,606 |
| $600 a month for 25 years | $469,825 | $224,391 |
| $600 a month for 30 years | $701,672 | $289,079 |
| $600 a month for 35 years | $1,026,848 | $364,925 |
| $600 a month for 40 years | $1,482,925 | $454,601 |
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, $500 a month: $155,552, $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.