$50 a month for 15 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $12,233 | $3,233 | $7,852 |
| 5% | $13,241 | $4,241 | $8,499 |
| 6% | $14,346 | $5,346 | $9,208 |
| 7% | $15,555 | $6,555 | $9,984 |
| 8% | $16,880 | $7,880 | $10,835 |
| 10% | $19,922 | $10,922 | $12,787 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $600 | $619 | $601 |
| 2 | $1,200 | $1,281 | $1,208 |
| 3 | $1,800 | $1,990 | $1,821 |
| 4 | $2,400 | $2,748 | $2,442 |
| 5 | $3,000 | $3,560 | $3,071 |
| 6 | $3,600 | $4,428 | $3,708 |
| 7 | $4,200 | $5,357 | $4,356 |
| 8 | $4,800 | $6,351 | $5,014 |
| 9 | $5,400 | $7,415 | $5,683 |
| 10 | $6,000 | $8,553 | $6,364 |
| 11 | $6,600 | $9,770 | $7,058 |
| 12 | $7,200 | $11,073 | $7,767 |
| 13 | $7,800 | $12,467 | $8,490 |
| 14 | $8,400 | $13,959 | $9,229 |
| 15 | $9,000 | $15,555 | $9,984 |
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 $50 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 | $4,867 | $6,252 | $7,885 |
| 15 years | $10,332 | $14,864 | $21,135 |
The middle of the simulation sits below the steady 7% figure of $15,555 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $15,555 would pay in retirement
At a 4% first-year withdrawal, $15,555 pays about $622 a year, $52 a month, before tax; in today’s dollars that is about $399 a year. How long a balance near it lasts at each withdrawal: how long $100,000 lasts. To stop saving early and let growth do the rest, see Coast FIRE numbers by age.
$600 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.
$50 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| $50 a month for 5 years | $3,560 | $3,071 |
| $50 a month for 10 years | $8,553 | $6,364 |
| 15 years | $15,555 | $9,984 |
| $50 a month for 20 years | $25,377 | $14,051 |
| $50 a month for 25 years | $39,152 | $18,699 |
| $50 a month for 30 years | $58,473 | $24,090 |
| $50 a month for 35 years | $85,571 | $30,410 |
| $50 a month for 40 years | $123,577 | $37,883 |
Other amounts for 15 years
$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, $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.