$300 a month for 5 years at returns from 4% to 10%
| Return | Balance | Of which growth | In today’s dollars |
|---|---|---|---|
| 4% | $19,854 | $1,854 | $17,126 |
| 5% | $20,344 | $2,344 | $17,549 |
| 6% | $20,846 | $2,846 | $17,982 |
| 7% | $21,359 | $3,359 | $18,424 |
| 8% | $21,883 | $3,883 | $18,877 |
| 10% | $22,968 | $4,968 | $19,813 |
Year by year at 7%
| Year | Put in so far | Balance | In today’s dollars |
|---|---|---|---|
| 1 | $3,600 | $3,714 | $3,606 |
| 2 | $7,200 | $7,688 | $7,247 |
| 3 | $10,800 | $11,940 | $10,927 |
| 4 | $14,400 | $16,490 | $14,651 |
| 5 | $18,000 | $21,359 | $18,424 |
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 $300 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) |
|---|---|---|---|
| 3 years | $10,341 | $11,999 | $13,794 |
| 5 years | $17,424 | $21,045 | $25,620 |
The middle of the simulation sits below the steady 7% figure of $21,359 because ups and downs cost compounding: a 20% loss needs a 25% gain to get back.
What $21,359 would pay in retirement
At a 4% first-year withdrawal, $21,359 pays about $854 a year, $71 a month, before tax; in today’s dollars that is about $737 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.
$3,600 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.
$300 a month for other terms
| Years | Balance | In today’s dollars |
|---|---|---|
| 5 years | $21,359 | $18,424 |
| $300 a month for 10 years | $51,316 | $38,184 |
| $300 a month for 15 years | $93,331 | $59,906 |
| $300 a month for 20 years | $152,261 | $84,303 |
| $300 a month for 25 years | $234,913 | $112,196 |
| $300 a month for 30 years | $350,836 | $144,540 |
| $300 a month for 35 years | $513,424 | $182,462 |
| $300 a month for 40 years | $741,463 | $227,300 |
Other amounts for 5 years
$50 a month: $3,560, $100 a month: $7,120, $150 a month: $10,679, $200 a month: $14,239, $250 a month: $17,799, $400 a month: $28,478, $500 a month: $35,598, $600 a month: $42,718, $750 a month: $53,397, $1,000 a month: $71,196, $1,500 a month: $106,794, $2,000 a month: $142,392, $2,500 a month: $177,990, $3,000 a month: $213,588, $5,000 a month: $355,979.
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.